Electrical Power Quality Analysis of the KGHM

Transcription

AGH – University of Science and Technology
Faculty of Electrical Engineering, Automatics, Computer Science
and Biomedical Engineering
Department of Power Electronics and Energy Conversion Systems
Automation
Postgraduate Studies
Electrical Power Quality
DIPLOMA THESIS
Electrical Power Quality Analysis of the KGHM PM S.A
Distribution System Operator Network
Name:
M.Sc. Eng. Radosław Rymkiewicz
Place of employment:
KGHM PM S.A.
Thesis supervisor:
Ph.D. Eng. Andrzej Firlit
Krakow 2012/2013
Contents
1
2
3
4
Introduction ............................................................................................................................ 2
Configuration of the KGHM PM S.A. Division DSO network .................................................. 2
The measurement points and rationale of their selection....................................................... 3
The measurements and their analysis ................................................................................... 4
4.1
Measurement I at the KGHM PM S.A. Division and the Company "A" feeder ................ 6
4.1.1
The measurement data ........................................................................................... 6
4.1.2
Analysis according to the standard PN-EN 50160 ................................................... 7
4.1.3
Correlation analysis ................................................................................................. 9
4.2
Conclusions drawn from the measurement No. I .......................................................... 11
4.3
Measurement II at the KGHM PM S.A. Division and the Company "B" feeder ............. 12
4.3.1
The measurement data ......................................................................................... 12
4.3.2
Analysis according to the standard PN-EN 50160 ................................................. 13
4.3.3
Correlation analysis ............................................................................................... 17
4.4
Conclusions drawn from the measurement No. II ......................................................... 19
4.5
Measurement III at the Company "C" feeder, the MV feed point .................................. 20
4.5.1
The measurement data ......................................................................................... 20
4.5.2
Analysis according to the standard PN-EN 50160 ................................................. 20
4.5.3
Correlation analysis ............................................................................................... 22
4.6
Conclusions drawn from the measurement No. III ........................................................ 23
5 Measures that should be taken to improve power quality - mitigation of voltage fluctuations
and power factor improvement............................................................................................ 24
5.1
Mitigation of voltage fluctuations (long-term flicker severity index Plt)........................... 24
5.2
Maintaining the required level of power factor tgφ ........................................................ 28
5.3
Summary and conclusions ............................................................................................ 29
References.................................................................................................................................. 30
1
1 Introduction
The objective of the thesis is to investigate the quality electrical of power in the KGHM
Polska Miedź S.A. Division network at selected external customers feed points, as well as at the
plant feeder at the medium voltage side. The network is operated by the KGHM Polska Miedź
S.A. Distribution System Operator. KGHM Polska Miedź S.A., while complying with provisions of
the Energy Law Act of April 10, 1997 (uniform text Dz.U. [Journal of Laws] 2012, item 1059) and
the Regulation of the Minister of Economy of May 4, 2007 on detailed conditions for the
operation of the power system (Dz.U. [Journal of Laws] No. 93, item 623 of May 29, 2007) shall
also, as the Distribution System Operator, be compliant with the requirements regarding the
quality of electrical power supply. The study was carried out according to the power quality
related standard: PN-EN 501601. It will be determined whether the quality of electrical power
supplied by the KGHM PM S.A. DSO meets the requirements of this standard, and solutions for
power quality improvement will be presented, if such improvement is needed.
2 Configuration of the KGHM PM S.A. Division DSO network
The Main Transformer Station supplying the KGHM PM S.A. Division, denoted as GST
110/6kV, is located at the Division site. It is supplied from two 110kV radial feeder lines: S-437
and S-438 from the 110kV substation operated by the TAURON Dystrybucja S.A. Company.
Under normal operating conditions the Division utilizes only a single 110kV feeder line while the
second feed point supplies the external Company "A". Such configuration allows avoiding
disturbances introduced to the plant grid in the case the Division and Company "A" are supplied
from the same transformer and improves security of supply. Where both plants are supplied from
the same transformer the security and reliability of supply are jeopardized: in the case of a
power failure in the 110kV line the Division is in danger of temporary shutdown, while a failure of
the cable supplying the Company "A" plant may result in the transformer emergency tripping off.
Considering the case of a power failure in one of the 110kV lines it has been decided that
after modification of connections both: the Division and Company "A" will be supplied from the
same transformer under the condition of limiting or shutdown the Company's "A" production
where necessary. Apart of the risk of power failures, each year in the summer season are
carried out maintenance works scheduled for three days, and during that period both: Division
and Company "A" plant are supplied from the same transformer.
It should be noted that it is not possible to provide independent feeders for each division
6kV substation and providing them with automatic stand-by switching at the 6kV level.
At the KGHM PM S.A. Division premises is located a coal/natural gas fired power plant,
owned by the Energetyka Company. The Division is connected with the power plant by means of
five 6kV feed points and one LV feed point. Normally the power plant utilizes generator No. 2;
generator No. 1 is only sporadically used; generator No. 3 is currently at the commissioning
phase and it was several times turned on for periods from several to over ten hours.
1
Polish Standard PN-EN 50160 "Voltage characteristics of electricity supplied by public distribution networks",
Warsaw, 2010.
2
A number of external consumers, bound by contracts for electric power supply with the
KGHM PM S.A. Division, are connected to the KGHM PM S.A. Division power grid. They are
mostly manufacturing companies, linked through capital ties with KGHM PM S.A., and
companies that provide services for the KGHM PM S.A Division.
3 The measurement points and rationale of their selection
The selected measurement points are shown in a schematic diagram of the KGHM PM
S.A. Division power network (Fig. 1). The pairs of measurements are marked with colours and
are assigned subsequent numbers.
Fig. 1 A schematic diagram of the KGHM PM S.A. Division power network
3
Considering the selection of measurement points the following factors were taken into
account:
Measurement I (7 days) - the measurement point at the Company "A" feeder was chosen
because of the presence of fluctuating loads, i.e. arc furnaces. Disturbances emitted by arc
furnaces will be examined at the measurement point at the Company "A" feeder, whereas the
purpose of measurement at the KGHM PM S.A. Division feeder is to determine the quality of
supply from Tauron S.A., check whether or not the disturbances generated within the KGHM PM
S.A. Division network and propagated from outside are influencing each other and if so, to what
extent, and also check if disturbances emitted by arc furnaces propagate through the 110kV side
to the Division power supply.
Measurement II (7 days) - its purpose is to measure power quality parameters at the KGHM
PM S.A. Division feeder at the medium voltage side and the Division's power system influence
(i.e. either worsening or improvement) on the quality of electric power sold to the Company "B",
and check if induction furnaces installed close to the external load have a significant influence on
the quality of electric power supplied to this external consumer.
Measurement III (7 days) - its purpose is to measure the quality of electric power sold to the
"C" consumer at the medium voltage side of the switchgear supplying several frequency
converters at both: the medium and low voltage sides. Investigation of the influence of
disturbances generated by frequency converters on the quality of power sold to the end
customer.
4 The measurements and their analysis
Measurements in the KGHM PM S.A. Division were carried out during the summer and
winter season by means of two power quality analysers from different manufacturers: C.A. 8335
Qualistar+ supplied by the French company Chauvin Arnoux (Fig. 2) and the domestic company
Sonel make PQM 701 (Fig. 3).
Fig. 2 Power quality analyser C.A. 8335 Qualistar+,
French company Chauvin Arnoux
4
Fig. 3 Power quality analyser PQM 701, Polish
company Sonel
The measurement arrangements are illustrated with photographs in figures 4 and 5
Fig. 4 An example of measurement using C.A. 8335 Qualistar+ analyser
Fig. 5 An example of measurement using PQM 701 analyser
5
4.1 Measurement I at the KGHM PM S.A. Division and the Company "A"
feeder
4.1.1 The measurement data
Measurement I, actually a pair of measurements, indicated in the diagram (Fig. 1) by
orange circles  was started on 22.06.2012. According to the standard the measurement
duration was 7 days and it was terminated on 29.06.2012. Since the measurements were carried
out using two different instruments, employing different software, the measurement data were
transferred to Microsoft Excel spreadsheet and processed according to the standard
requirements in order to achieve clear analysis results. Also a correlation analysis of power
quality parameters was performed2 using the Pearson coefficient of correlation for all
measurement points.
The analysis results are included in succeeding subsections. Figures 6 and 7 show
example time characteristics obtained by means of the analysers' software.
Fig. 6 - An example time characteristic of rms
voltage value recorded using the C.A. 8335
Qualistar analyser software
2
Fig. 7 An example time characteristic of rms voltage
value recorded using the PQM 701 analyser software
K. Chmielowiec "Obróbka statystyczna wyników"; AGH-UST, Krakow 2012.
6
4.1.2 Analysis according to the standard PN-EN 50160
Company "A"
Fig. 8 Schematic diagram of the KGHM PM S.A. Division power network – measurement I
The analysis below takes into account solely the parameters whose values are not compliant
with the standard requirements.
4.1.2.1
Long-term flicker indicator Plt
At least 95.00% of values shall be contained within the interval 0.00 - 1.00.
95%
3,00
3,00
Plt L1
Plt L1
2,50
2,50
Plt L2
Plt L2
Plt L3
Plt L3
2,00
95% of values contained within the
interval from 0 to 1
interval from 0 to1
2,00
1,50
1,50
1,00
1,00
0,50
0,00
00
.0
01
00
.0
45
0:
time
Fig. 9 Long-term flicker indicator Plt - Measurement I
– the Company "A" Criterion: 95% of values
contained within the interval from 0 to 1
82
79
76
73
70
67
64
61
58
55
52
49
46
43
40
37
34
31
28
25
22
19
16
7
13
4
10
0,00
1
.0
6.
28
22
:0
00
.0
47
0:
10
:0
28
.0
6.
20
12
00
.1
54
0:
22
:0
27
.0
6.
20
12
00
.1
31
0:
10
:0
27
.0
6.
20
12
00
.0
69
0:
22
:0
26
.0
6.
20
12
00
.0
87
0:
10
:0
26
.0
6.
20
12
00
.1
03
0:
22
:0
25
.0
6.
20
12
00
.0
59
0:
0:
10
:0
25
.0
6.
20
12
00
.1
83
22
:0
24
.0
6.
20
12
00
.1
88
0:
10
:0
24
.0
6.
20
12
00
.0
74
0:
0:
22
:0
23
.0
6.
20
12
00
.1
61
.0
6.
20
12
23
10
:0
0:
22
:0
20
12
22
.0
6.
.0
6.
20
12
20
12
22
10
:0
0:
00
.1
13
0,50
sample
Fig. 10 Long-term flicker indicator
Plt - Measurement I - the Company "A" Criterion: 95%
of values contained within the interval from 0 to1;
samples arranged in ascending order
7
8
2012.06.29 05:10:00.014
2012.06.29 00:20:00.034
2012.06.28 19:30:00.191
2012.06.28 14:40:00.178
2012.06.28 09:50:00.080
2012.06.28 05:00:00.122
2012.06.28 00:10:00.071
2012.06.27 19:20:00.052
2012.06.27 14:30:00.043
2012.06.27 09:40:00.110
2012.06.27 04:50:00.146
L2
2012.06.27 00:00:00.132
2012.06.26 19:10:00.028
2012.06.26 14:20:00.087
2012.06.26 09:30:00.144
2012.06.26 04:40:00.100
2012.06.25 23:50:00.191
L1
2012.06.25 19:00:00.129
2012.06.25 14:10:00.015
2012.06.25 09:20:00.017
2012.06.25 04:30:00.120
2012.06.24 23:40:00.131
20
12
.0
6.
22
20
12
08
.0
:5
6.
0:
22
20
00
12
.1
16
21
.0
:2
6.
0:
22
20
00
12
.0
23
94
.0
:
50
6.
:0
23
20
0.
12
07
06
.0
:
7
2
6.
0:
23
20
00
12
.1
14
84
.0
:5
6.
0:
23
20
00
12
.0
22
58
.0
:2
6.
0:
24
20
00
12
.0
05
15
.0
:5
6.
0
:0
24
20
0.
12
13
11
.0
:2
7
6.
0
:0
24
20
0.
12
20
00
.0
:5
7
6.
0
:
25
20
00
12
.0
04
66
.0
:2
6.
0:
25
20
00
12
.1
11
83
.0
:5
6.
0:
25
20
00
12
.1
19
52
.0
:2
6.
0:
26
20
00
12
.0
02
29
.0
:5
6.
0:
26
20
00
12
.0
10
07
.0
:2
6.
0
:0
26
20
0.
12
17
07
.0
:5
8
6.
0
:0
27
20
0.
12
01
11
.0
:2
1
6.
0:
27
20
00
12
.1
08
50
.0
:5
6.
0:
27
20
00
12
.1
16
75
.0
:2
6.
0:
27
20
00
12
.0
23
61
.0
:5
6.
0:
28
20
00
12
.0
07
40
.0
:2
6.
0
:0
28
20
0.
12
14
19
.0
:5
0
6.
0
:0
28
20
0.
12
22
07
.0
:2
9
6.
0
:0
29
0.
05
08
:5
1
0:
00
.1
09
1,00
2012.06.24 18:50:00.053
2012.06.24 14:00:00.086
2012.06.24 09:10:00.031
2012.06.24 04:20:00.060
2012.06.23 23:30:00.147
2012.06.23 18:40:00.084
2012.06.23 13:50:00.123
2012.06.23 09:00:00.102
2012.06.23 04:10:00.082
2012.06.22 23:20:00.057
2012.06.22 18:30:00.044
2012.06.22 13:40:00.104
2012.06.22 08:50:00.121
kV
Numbers of samples meeting the above criterion:
Plt Company "A"
L3
66.25% 68.75% 66.25%
Table 1 - The percentage contribution of samples meeting the standard PN-EN 50160 criterion for long-term
flicker indicator Plt for the Company "A"
4.1.2.2 Power factor tgφ
1,20
tg φ= 0,4
tg φ Σ average
0,80
0,60
0,40
0,20
0,00
time
Fig. 11 Time characteristic of tgφ - measurement I - the Company "A"
The KGHM PM S.A. Division
4.1.2.3 Long-term flicker indicator Plt
6,60
6,40
6,20
6,00
5,80
U1
U2
U3
U1min
U2min
U3min
U1max
U2max
U3max
5,60
5,40
time
Fig. 12 Voltage magnitude time characteristic – Measurement I - the KGHM PM S.A. Division
rms values – average, min., max.
95%
3,00
3,00
Plt L1
2,50
Plt L1
2,50
Plt L2
Plt L2
Plt L3
2,00
Plt L3
interval from 0 to1
2,00
1,50
1,50
1,00
1,00
0,50
0,00
01
45
22
:0
0
:0
0
.0
47
.2
8
10
:0
0
:0
0
.0
82
79
76
73
70
67
64
61
58
55
52
49
46
43
40
37
34
31
28
25
22
19
16
13
7
10
20
4
12
.0
6
0,00
1
54
20
12
.0
6
.2
8
22
:0
0
:0
0
.0
31
20
12
.0
6
.2
7
10
:0
0
:0
0
.1
69
.1
.2
7
20
12
.0
6
.2
6
22
:0
0
:0
0
.0
87
20
12
.0
6
.2
6
10
:0
0
:0
0
.0
03
20
12
.0
6
.2
5
22
:0
0
:0
0
.1
59
20
12
.0
6
.2
5
10
:0
0
:0
0
.0
83
20
12
.0
6
.2
4
22
:0
0
:0
0
.1
88
20
12
.0
6
.2
4
10
:0
0
:0
0
.1
74
20
12
.0
6
.2
3
22
:0
0
:0
0
.0
61
.1
:0
0
.0
6
12
20
20
12
.0
6
.2
3
10
:0
0
:0
0
:0
0
22
.2
2
.0
6
12
20
20
12
.0
6
.2
2
10
:0
0
:0
0
.1
13
0,50
sample
time
Fig. 13 Long-term flicker indicator Plt - Measurement I –
the KGHM PM S.A. Division;
Criterion: 95% of values contained within the interval
from 0 to 1
Plt - Measurement I - the KGHM PM S.A. Division;
from 0 to1;
Plt KGHM PM S.A. Division
L1
L2
L3
67.50% 68.75% 68.75%
flicker indicator Plt for the KGHM PM S.A. Division
4.1.3 Correlation analysis
Company "A"
3,50
Correlation between Plt and P
3,00
Liniowy (Correlation between Plt and P)
2,50
Fig. 15 Correlation between Plt
and P - Measurement I - the
Company "A"
Plt
2,00
1,50
1,00
0,50
correlation coefficient 0,87
0,00
0
1
2
3
4
5
6
P
9
3,50
Correlation between Plt and Q
Liniowy (Correlation between Plt and Q)
3,00
2,50
and Q - Measurement I - the
KGHM PM S.A. Division
Plt
2,00
1,50
1,00
0,50
0,00
0
0,5
1
1,5
2
2,5
3
3,5
Q
3,00
2,50
Plt
2,00
and P - Measurement I - the
1,50
1,00
0,50
0,00
0
2
4
6
8
10
12
14
16
P
3,00
2,50
Plt
2,00
and Q - Measurement I - the
1,50
1,00
0,50
correlation coefficient -0,10
0,00
0
0,5
1
1,5
2
Q
10
2,5
3
3,5
4
Correlation of Plt between the Company "A" and the KGHM PM S.A. Division
3,00
Correlation of Plt between the Company A and the KGHM PM S.A. Division
2,50
Liniowy (Correlation of Plt between the Company A and the KGHM PM S.A. Division)
Plt Company A
2,00
1,50
1,00
0,50
0,00
0,00
0,50
1,00
1,50
2,00
2,50
3,00
Fig. 19 Correlation of Plt between the Company "A" and the KGHM PM S.A. Division
4.2 Conclusions drawn from the measurement No. I
The summary of analysis of measurements at the measurement point No. I is provided in
table below:
Table 3 Power quality parameters at the measurement point No. I according to standard PN-EN 50160
The analysis of power quality parameters at the measurement point No. 1 shows that the
key problem is the failure to comply with the requirements of standard PN-EN 50160 concerning
the long-term flicker indicator Plt. Measurements at both: the KGHM PM S.A. Division and
Company’s "A" feeders revealed results exceeding the limit values. Voltage fluctuations can be
easily seen from the voltage magnitude time characteristic (Fig. 12). The correlation analysis
allows concluding that the part responsible for this situation is the consumer - the Company "A",
which operates electric arc furnaces. The correlation between reactive and active powers and
11
long-term flicker severity Plt at the Company "A" feed point is evident. In the case of the KGHM
PM S.A. Division the measurements show no correlation. Furthermore, the P lt analysis
performed for both feed points shows a noticeable relation. The correlation coefficient is close to
unity.
It is, therefore, apparent that the cause of worsening the long-term flicker index Plt are arc
furnaces installed at the Company "A" plant. Proposed solutions for that problem are discussed
in section 5.
The analysis also shows that the power factor value at the Company "A" feed point is
exceeded. According to the provisions of the connection agreement between the KGHM and
TAURON S.A. the power factor is calculated as the sum of the transformer T1 and transformer
T2 power factors, thus the Division power system dispatchers are controlling capacitor banks so
as to prevent exceeding the value 0.4 set forth in the agreement. The Central System for
Electricity Balancing and Settlement enables online monitoring of power network parameters,
i.e.: active power, reactive power and power factor. The staff can, therefore, monitor the Division
network on a continuous basis. The manual operation of capacitor banks should undoubtedly be
supplanted by automatic control.
4.3 Measurement II at the KGHM PM S.A. Division and the Company "B" feeder
The second pair of measurements indicated in the diagram by violet circles  was started
on 06.07.2012. According to the standard the measurement duration was 7 days and it was
terminated on 29.06.2012. As formerly, the measurement data were transferred to Microsoft
Excel spreadsheet and processed according to the standard requirements and for the purposes
of correlation analysis. The analyses' results are included in succeeding subsections. In the
succeeding subsections solely the parameters whose values are not compliant with the standard
requirements are provided.
12
Company "B"
Fig. 20 Schematic diagram of the KGHM PM S.A. Division power network – measurement II
4.3.2.1
Long-term flicker indicator - Plt
95%
1,60
1,6
PLT L1
Plt L1
1,4
1,40
Plt L2
PLT L2
Plt L3
PLT L3
1,2
1,20
interval from 0 to1
1
Plt
1,00
Plt
0,8
0,80
0,6
0,60
0,4
0,40
0,2
0,20
25
82
79
76
73
70
67
64
61
58
55
52
49
46
43
40
37
34
31
28
25
22
19
16
7
13
4
10
1
.1
10
:0
0
:0
0
04
0,00
sample
20
12
.0
7
.1
3
16
:0
0
:0
0
.1
96
27
20
12
.0
7
.1
2
04
:0
0
:0
0
.0
32
20
12
.0
7
.1
2
16
:0
0
:0
0
.0
72
.0
:0
0
:0
0
04
.1
1
.0
7
12
20
20
12
.0
7
.1
1
16
:0
0
:0
0
.1
62
01
20
12
.0
7
.1
0
04
:0
0
:0
0
.0
03
20
12
.0
7
.1
0
16
:0
0
:0
0
.1
96
20
12
.0
7
.0
9
04
:0
0
:0
0
.1
73
.0
:0
0
:0
0
16
.0
9
.0
7
12
20
20
12
.0
7
.0
8
04
:0
0
:0
0
.1
51
20
.0
20
12
.0
7
.0
8
16
:0
0
:0
0
.1
:0
0
:0
0
04
.0
7
20
12
.0
7
.0
7
.0
7
12
20
20
12
.0
7
.0
6
16
:0
0
:0
0
.0
06
0
time
Fig. 21 Fig. Long-term flicker indicator
Plt - Measurement II – the Company "B"
from 0 to 1
Fig. 22 - Fig. Long-term flicker indicator
Plt - Measurement II - the Company "B"
Criterion: 95% of values contained within the
interval from 0 to1; samples arranged in
13
ascending order
Plt Company "B"
L1
L2
L3
93.75% 91.25% 92.50%
Table 4 – T he percentage contribution of samples meeting the standard PN-EN 50160 criterion for longterm flicker indicator Plt - Company "B"
4.3.2.2 Events – voltage swells, dips, short supply interruptions, long supply interruptions
During the measurement a single disturbance has occurred: a voltage dip in the phase U2. Date
and time of the occurrence: 11.07.2012, 4:23:45 am; duration 0.110 s.
The event was recorded in the power network dispatcher logbook:
"4:22 am – a voltage dip occurred in the line S-438. The Plant Dispatch Centre informed that the
dip source was the external 110 kV line".
Fig. 23 The record of voltage dip waveforms and data; instantaneous values – measurement II – Company
"B"
Fig 24 The record of voltage dip waveforms and data; rms voltage values– measurement II - Company "B"
14
2012.07.13 12:00:00.110
2012.07.13 07:10:00.116
2012.07.13 02:20:00.120
2012.07.12 21:30:00.197
2012.07.12 16:40:00.081
2012.07.12 11:50:00.159
2012.07.12 07:00:00.028
2012.07.12 02:10:00.182
2012.07.11 21:20:00.124
2012.07.11 16:30:00.166
2012.07.11 11:40:00.065
2012.07.11 06:50:00.038
2012.07.11 02:00:00.198
2012.07.10 21:10:00.154
2012.07.10 16:20:00.120
2012.07.10 11:30:00.171
2012.07.10 06:40:00.058
2012.07.10 01:50:00.175
2012.07.09 21:00:00.124
2012.07.09 16:10:00.177
2012.07.09 11:20:00.174
2012.07.09 06:30:00.021
2012.07.09 01:40:00.052
2012.07.08 20:50:00.056
2012.07.08 16:00:00.096
2012.07.08 11:10:00.143
2012.07.08 06:20:00.180
2012.07.08 01:30:00.048
2012.07.07 20:40:00.109
2012.07.07 15:50:00.156
2012.07.07 11:00:00.178
2012.07.07 06:10:00.095
2012.07.07 01:20:00.059
2012.07.06 20:30:00.037
2012.07.06 15:40:00.129
kV
.0
7.
20
06
12
15
.0
:5
7.
0:
20
06
00
12
23
.1
.0
22
:2
7.
0:
20
07
00
12
06
.0
.0
05
:5
7.
0:
20
07
00
12
14
.1
.0
84
:2
7.
0:
20
07
00
12
21
.0
.0
03
:5
7.
0:
20
08
00
12
05
.1
.0
52
:2
7.
0
20
08
:0
0.
12
12
13
.0
:5
2
7.
0
20
08
:0
0.
12
20
04
.0
:2
0
7.
0
20
09
:0
0.
12
03
00
.0
:5
1
7.
0:
20
09
00
12
11
.1
.0
38
:2
7.
0:
20
09
00
12
18
.1
.0
74
:5
7.
0:
20
10
00
12
02
.0
.0
98
:2
7.
0:
20
10
00
12
09
.1
.0
74
:5
7.
0:
20
10
00
12
17
.0
.0
23
:2
7.
0
20
11
:0
0.
12
00
01
.0
:5
5
7.
0
20
11
:0
0.
12
08
02
.0
:2
2
7.
0
20
11
:0
0.
12
15
11
.0
:5
7
7.
0:
20
11
00
12
23
.1
.0
82
:2
7.
0:
20
12
00
12
06
.0
.0
35
:5
7.
0:
20
12
00
12
14
.0
.0
27
:
2
7.
0:
20
12
00
12
21
.0
.0
80
:5
7.
0:
20
13
00
12
05
.0
.0
35
:2
7.
0:
13
00
12
.1
88
:5
0:
00
.1
63
20
12
tgφ
4.3.2.3 power factor tgφ
2,50
2,00
tg φ= 0,4
tg φ Σ average
1,50
1,00
0,50
0,00
time
Fig. 25 Time characteristic of tgφ - measurement I - the Company "B"
(Common power supply with the Company "A" from a single transformer - the analyser is measuring only
the Division’s power supply).
4.3.2.4 Long-term flicker indicator - Plt
6,600
6,400
6,200
6,000
5,800
5,600
U1
U2
U3
U1min
U2min
U3min
U1max
U2max
U3max
5,400
5,200
5,000
time
Fig. 26 Voltage magnitude time characteristic – Measurement II - the KGHM PM S.A. Division; Voltage rms
values – average, min., max.
15
1,80
Plt L1
1,80
Plt L2
1,60
95%
2,00
2,00
Plt L1
Plt L3
Plt L2
1,60
1,40
Plt L3
1,40
Plt
1,20
1,00
interval from 0 to1
1,20
Plt
0,80
1,00
0,60
0,40
0,80
0,20
0,60
0,00
20
12
.0
7.
06
16
20
:0
12
0:
.0
00
7.
.0
07
06
04
20
:0
12
0
:0
.0
0.
7.
12
07
0
16
20
:0
12
0:
.0
00
7.
.0
08
51
04
20
:0
12
0:
.0
00
7.
.1
08
73
16
20
:0
12
0:
.0
00
7.
.
09
09
6
04
20
:0
12
0:
.0
00
7.
.1
09
03
16
20
:0
12
0:
.0
00
7.
.1
10
01
04
20
:0
12
0:
.0
00
7.
.
06
10
2
16
20
:0
12
0:
.0
00
7.
.1
11
72
04
20
:0
12
0:
.0
00
7.
.0
11
32
16
20
:0
12
0:
.0
00
7.
.
02
12
7
04
20
:0
12
0:
.0
00
7.
.0
12
96
16
20
:0
12
0:
.0
00
7.
.1
13
10
04
:0
0:
00
.1
25
0,40
0,20
0,00
82
79
76
73
70
67
64
61
58
55
52
49
46
43
40
37
34
31
28
25
22
19
16
13
7
10
4
1
time
sample
Plt - Measurement II – the KGHM PM S.A. Division
Plt - Measurement II - the KGHM PM S.A. Division: 95% of
values contained within the interval from 0 to1; samples
arranged in ascending order
Plt the KGHM PM S.A. Division
L1
L2
L3
91.25%
93.75%
91.25%
Table 5 The percentage contribution of samples meeting the standard PN-EN 50160 criterion for long-term
flicker indicator Plt - the KGHM PM S.A. Division
4.3.2.5 Events – voltage swells, dips, short supply interruptions, long supply interruptions
During the measurement a single disturbance has occurred: a voltage dip in the phase U2. Date
and time of the occurrence: 11.07.2012, 4:23:45 am; duration 0.110 s.
7.000
6.500
kV
6.000
5.500
5.000
4.500
2012-07-10
13:54:40.000
1:04:40:39 (d:h:min:s)
5 h/Div
2012-07-11
18:35:19.111
Fig. 29 The record of voltage dip waveforms; rms voltage values (average, min., max.) –
measurement II - the KGHM PM S.A. Division
(The rms max. and min. values are computed every half-cycle, averaging time: 10 minutes)
16
Company "B"
1,60
1,40
1,20
Fig. 30 Correlation between
Plt and P - Measurement II –
Company "B"
Plt
1,00
0,80
0,60
0,40
0,20
0,00
0,00
0,01
0,01
0,02
0,02
0,03
0,03
0,04
0,04
0,05
P
1,60
1,40
1,20
Plt
1,00
Plt and Q - Measurement
II - Company "B"
0,80
0,60
0,40
0,20
0,00
0
0,01
0,02
0,03
0,04
0,05
0,06
0,07
Q
1,80
1,60
1,40
1,20
Plt and P - Measurement II –
the KGHM PM S.A. Division
Plt
1,00
0,80
0,60
0,40
0,20
0,00
0,00
2,00
4,00
6,00
8,00
10,00
12,00
14,00
16,00
P
17
1,80
1,60
1,40
Fig 33 Correlation between Plt
and Q - Measurement II – the
1,20
Plt
1,00
0,80
0,60
0,40
0,20
0,00
0,00
0,50
1,00
1,50
2,00
2,50
3,00
Q
Correlation of Plt between the Company "B" and the KGHM PM S.A. Division
1,80
1,60
Correlation of Plt between the Company B and the KGHM PM S.A. Division
Liniowy (Correlation of Plt between the Company B and the KGHM PM S.A. Division)
1,40
1,20
1,00
0,80
0,60
0,40
0,20
0,00
0,00
0,20
0,40
0,60
0,80
1,00
1,20
1,40
1,60
Plt Company B
Fig. 34 Correlation of Plt between the Company "B" and the KGHM PM S.A. Division
18
4.4 Conclusions drawn from the measurement No. II
The summary of analysis of measurements at the measurement point No. II is provided in table
below:
Table 6 Power quality parameters at the measurement point No. II according to standard PN-EN 50160
The analysis of power quality parameters at the measurement point No. II shows that the
key problem is the failure to comply with the requirements of standard PN-EN 50160 concerning
the long-term flicker indicator Plt. Measurements at both: the KGHM PM S.A. Division and
Company’s "B" feeders revealed results exceeding the limit values. The correlation analysis
allows concluding that neither the Company "B" nor the KGHM PM S.A. Division are the sources
of voltage fluctuations. In this configuration the KGHM PM S.A. Division was supplied from the
same transformer as the Company "A", but the measurement range comprised only the
Division’s feed point. Thus disturbances that result in exceeding the flicker severity limit are
present in the network but the measured circuits are not their sources. Nevertheless there is a
noticeable relation between the Company "B" flicker severity Plt and changes in the KGHM PM
S.A. Division Plt. We should therefore, focus on improving the long-term flicker severity index Plt
at the Company's "A" feeder (this is already known from the former conclusions, cf. section 4.2).
It should be noted that when the KGHM PM S.A. Division and Company's "A" are fed from the
same transformer, the Company "A" limits its output. Such solution improves security of supply
and, as can be seen from the measurement results, limits the long-term flicker severity index Plt.
The analysis shows also that the power factor value at the Company's "B" feed point is
exceeded. The Company "B" is not a large consumer of electric power; nevertheless
consideration should be given to reactive power compensation in order to improve power quality
factors (see section 5).
During the measurement a single voltage dip has occurred. Date and time of the voltage
dip occurrence: 11.07.2012, 4:23:45 am; duration 0.110 s. The voltage dip parameters are
shown in figures 23, 24 and 29. The voltage dip was an external event and the party responsible
for it is the supplier of electric power, i.e. TAURON S.A. It should be, however, noted that such
events at the feed point with TAURON S.A. are extremely rare and supply interruptions are
contained with limits set forth in the connection agreement and the contract for electric power
supply.
19
No significant influence of induction furnaces installed close to the external consumer (the
Company "B") on electric power quality parameters was observed.
Installation of power quality recorders in outgoing feeders to large electric power
consumers such as the Company "A" or the Company "B" should be considered. Alternatively a
portable instrument can be used which would provide necessary data depending on the nature
of problems arising in the power network and location of their occurrence.
4.5 Measurement III at the Company "C" feeder, the MV feed point
Measurement III indicated in the diagram by a green circle  was started on 21.01.2013.
According to the standard the measurement duration was 7 days and it was terminated on
28.01.2013. The measurement data were transferred to Microsoft Excel spreadsheet, processed
according to the standard requirements and their correlation analysis was performed. As
formerly, solely the parameters whose values are not compliant with the standard requirements
are provided.
Company "C"
Fig. 35. Schematic diagram of the KGHM PM S.A. Division power network – measurement III
20
4.5.2.1 Long-term flicker indicator - Plt
6600
6400
U1
U2
U3
U1max
U2max
U3max
U1min
U2min
U3min
V
6200
6000
5800
5600
09:00:00
04:10:00
23:20:00
18:30:00
13:40:00
08:50:00
04:00:00
23:10:00
18:20:00
13:30:00
08:40:00
03:50:00
23:00:00
18:10:00
13:20:00
08:30:00
03:40:00
22:50:00
18:00:00
13:10:00
08:20:00
03:30:00
22:40:00
17:50:00
13:00:00
08:10:00
03:20:00
22:30:00
17:40:00
12:50:00
08:00:00
03:10:00
22:20:00
17:30:00
12:40:00
5400
time
Fig. 36. Voltage magnitude time characteristic – measurement III - the Company "C"
rms voltage values – average, min., max.
2,50
Plt L1
95%
Plt L1
2,50
Plt L2
Plt L2
Plt L3
Plt L3
95% of values contained within the interval from 0 to 1
82
79
76
73
70
67
64
61
58
55
52
49
46
43
40
37
34
31
28
0,00
25
0,00
14:30:00 02:00:00 14:00:00 02:00:00 14:00:00 02:00:00 14:00:00 02:00:00 14:00:00 02:00:00 14:00:00 02:00:00 14:00:00 02:00:00
time
22
0,50
19
0,50
16
1,00
13
1,00
10
1,50
7
1,50
95% of values contained within the interval from 0 to1
4
2,00
1
2,00
sample
Plt - measurement III – the Company "C"
Plt - measurement III - the Company "V"
from 0 to1;
The number of samples meeting the above criterion:
Plt Company "C"
L1
L2
L3
100%
0.0%
0.0%
flicker indicator Plt – the Company "C"
21
4.5.2.2 Power factor tgφ
6
tg φ= 0,4
tg φ Σ average
5
tgφ
4
3
2
1
12
:4
16 0:0
:5 0
21 0:0
:0 0
01 0:0
:1 0
05 0:0
:2 0
09 0:0
:3 0
13 0:0
:4 0
17 0:0
:5 0
22 0:0
:0 0
02 0:0
:1 0
06 0:0
:2 0
10 0:0
:3 0
14 0:0
:4 0
18 0:0
:5 0
23 0:0
:0 0
03 0:0
:1 0
07 0:0
:2 0
11 0:0
:3 0
15 0:0
:4 0
19 0:0
:5 0
00 0:0
:0 0
04 0:0
:1 0
08 0:0
:2 0
12 0:0
:3 0
16 0:0
:4 0
20 0:0
:5 0
01 0:0
:0 0
05 0:0
:1 0
09 0:0
:2 0
13 0:0
:3 0
17 0:0
:4 0
21 0:0
:5 0
02 0:0
:0 0
06 0:0
:1 0
10 0:0
:2 0
14 0:0
:3 0
18 0:0
:4 0
22 0:0
:5 0
03 0:0
:0 0
07 0:0
:1 0
11 0:0
:2 0
0:
00
0
time
Fig. 39 Time characteristic of tgφ - measurement III - the Company "C"
1,60
1,40
1,20
Plt
1,00
Plt and P - Measurement III,
Company "C"
0,80
0,60
0,40
correlation coefficient - 0,15
0,20
0,00
0,000
0,010
0,020
0,030
0,040
0,050
0,060
0,070
P
1,60
1,40
1,20
Plt
1,00
Plt and Q - Measurement III,
Company "C"
0,80
0,60
0,40
correlation coefficient - 0,15
0,20
0,00
0,000
0,020
0,040
0,060
0,080
Q
22
0,100
0,120
0,140
4.6 Conclusions drawn from the measurement No. III
The summary of analysis of measurements at the measurement point No. I is provided in table
below:
Table 8 Power quality parameters at the measurement point No. III according to standard PN-EN 50160
The analysis of power quality parameters at the third measurement point shows that the
key problem are exceeded limit values of the long-term flicker severity index Plt and power
factor. Thus, in order to reduce tgφ, reactive power compensation should be implemented. The
proposed measures for flicker severity index Plt improvement are described in section 5.
It is interesting that frequency converters supplied from the same switchgear - connected
at both: the low-voltage and medium-voltage side, have no significant influence on harmonic
content.
23
5 Measures that should be taken to improve power
quality - mitigation of voltage fluctuations and power factor
improvement
5.1 Mitigation of voltage fluctuations (long-term flicker severity index Plt)
Voltage fluctuations produce various effects that may adversely impact production
processes, equipment operation and human health, “namely:
- Voltage fluctuations at the terminals of induction motors cause changes in torque and slip, and
consequently affect the production process. In the worst case they may lead to excessive
vibration, reducing mechanical strength and shortening the motor service life.
- In electrolysers both the useful life and the operational efficiency of equipment can be reduced
in the presence of voltage fluctuations, process effectiveness can be reduced and product
quality deteriorated.
- Any change in supply voltage magnitude results in a change in the luminous flux of a light
source. This is known as flicker, which is a subjective visual impression of unsteadiness of a
light’s flux, when its luminance or spectral distribution fluctuates with time…The flicker caused by
voltage fluctuations significantly impairs vision and causes general discomfort and fatigue…
Flicker affects the vision process and human brain reaction. Flickering light sources can produce
discomfort and deterioration in work quality, in extreme cases can be the cause of accidents in
the workplace or epileptic seizures."4
If arc furnaces, connected as close to the HV/MV transformer as possible, are the cause
of exceeding the flicker severity Plt limit at the terminals of KGHM PM S.A. Division loads it
means, that voltage fluctuations propagate through the transformer and HV feed points. In that
case the remedy measures are both difficult and costly. The following solutions can be
considered:

Increasing the network short-circuit capacity by installation of a new HV/MV transformer
supplying arc furnaces. Since voltage fluctuations propagate through the 110 kV feed
point in the Tauron S.A. station, the transformer should be supplied from a different
110 kV station or, where possible, from a different busbars system in the existing 110 kV
station.

Limiting reactive power changes by means of additional power factor compensation at the
arc furnace point of connection. A follow-up compensator mitigates quick fluctuations,
although only to a limited extent. Slow voltage fluctuations should be less perceptible.

Another solution may consist in agreeing with the arc furnaces operator the time of
furnaces operation. In other words the furnaces should be operated during the feeder
least loading periods; consequently effects of voltage fluctuations will be minimized.
"Appropriate electrode positioning control, segregation and preliminary preparation of
furnace charge, the use of doped electrodes, etc."4 may considerably reduce voltage
fluctuations.
While considering these solutions both: the economic conditions and difficulty of installation shall
be accounted for.
4
Joint publication "Poradnik Inżyniera Elektryka" vol. 3 Wydawnictwa Naukowo-Techniczne, 4th edition, Warsaw
2011; p. 832-835
24

The first solution is extremely costly since it requires installing an additional transformer
that should be supplied from a different 110kV station than the one presently supplying
the plant or, if practicable, from a different busbars system in the existing 110 kV Tauron
S.A. station. An investment project, being currently implemented in the KGHM PM S.A.
Division assumes the Company "A" will be supplied from a separate transformer. It is now
in the design phase. The installation of a new transformer is first of all dictated by
improvement of the supply reliability. It should be thus analysed if there is a possibility of
supplying the new transformer from separate 110kV busbars. If such solution turns out to
be reasonably practicable the additional cost would be relatively small in terms of the
already commenced investment project. It should be emphasised that this solution will
remedy the problem at the Division feed point but for other consumers, supplied from the
same point of transformer connection at the Company "A" feeder, the problem will not be
resolved.

The second solution may be implemented independently from the first one because
mitigation of voltage fluctuations at the 110kV busbars will improve not only the quality of
the Division power supply but also of other consumers supplied from the Tauron S.A.
station.
Examples of solutions to the considered problem are illustrated in Fig. 42 that shows
classification of follow-up voltage stabilisers.
Follow-up reactive power compensators
Dynamic voltage stabilisers
Static
Rotating
(Synchronous machine)
Power electronic systems
Saturable reactors
25
Fig. 42 Classification of follow-up voltage stabilisers (older solutions, presently rarely used, are shaded in
4
grey)
In the subject literature can be found many configurations of static compensators.
"The most popular version is STATCOM compensator which is particularly effective in
reduction of voltage fluctuations produced by fluctuating loads".4 The circuit diagram and
phasor diagrams of a STATCOM compensator are shown in Fig. 43.
Fluctuating
load
VSC
Fig. 43 The STATCOM compensator: a) schematic diagram; phasor diagrams for various relationships
4
between U and Uvsc
Where:
Uvsc - voltage at the VSC converter input terminals
U - voltage at the supply busbars
Ux - voltage drop across the reactance Xr
I - the compensator current
Xr – the reactance of the VSC converter input reactor
Figure 44 shows an example installation of a cheaper D-STATCOM compensator that is a
perfect solution in the case of an arc furnace producing very strong voltage fluctuations.
4
Joint publication "Poradnik Inżyniera Elektryka" vol. 3; Wydawnictwa Naukowo-Techniczne, 4th edition, Warsaw
2011; p. 836-838
26
Fig. 44 A compact D-STATCOM application to an arc furnace
- schematic diagram
5
"…it should be emphasised that implementation of D-STATCOM compensators requires much
lower capital investments and their pay-back time is shorter than that of STATCOM
compensators in transmission systems. Thus, besides large companies like Siemens, Toshiba,
Mitsubishi Electric, Alstom, also smaller companies are entering the market. In Poland also
domestic companies provide installation of D-STATCOM compensators.”5
It should be borne in mind that STATCOM applications are expensive and can be
supplanted by a thyristor controlled reactor with fixed capacitor bank (FC/TCR). It is much
cheaper solution, which in our case will perform sufficiently well.
"The fixed capacitor bank (FC) with inductive current fundamental harmonic controller (TCR) is
an example of the indirect compensation method in which, depending on the needs of the
voltage restorer or the reactive power compensator function, the value of the sum of two current
components is controlled (Fig. 45):
 the capacitor current iFC fundamental harmonic; the capacitor bank normally is operated
as high harmonic filter(s) or a switched capacitor bank (TCR/TSC system);
 fundamental harmonic of the reactor current iTCR is controlled by means of a phasecontrolled thyristor AC switch (T).
Figure 45a shows a single-line diagram of such installation and Figure 45b shows the reactor
current waveforms for different values of the control angle α (with respect to voltage zerocrossing). The control angle and, consequently, the reactor current fundamental harmonic and
the compensator current fundamental harmonic values (as well as the value and sign of voltage
drop across the power system impedance) can vary during every half-cycle taking its values
from the interval (0.5π; π)”8.
PCC
Load
Fig. 45. a) Single-line equivalent diagram of the FC/TCR compensator; b) The voltage and current
waveforms that illustrate its principle of operation
5
R.Strzelecki, G.Benysek "Układy STATCOM i ich rola w systemie elektroenergetycznym"; Uniwersytet
Zielonogórski 2004; p. 11
8
Z. Hanzelka "Automatyka - Elektryka - Zakłócenia nr 5/2011"; WWW.ELEKTRO-INNOWACJE.PL
27
Power
supply
network
Load
Control
circuit
reference voltage/
reactive current
Fig 46 Schematic diagram of the FC/TCR compensator a closed-loop control system of the FC/TCR
compensator

The third solution seems to be the cheapest one. It however requires the arc furnaces
operator to comply with some requirements concerning segregation and preliminary
preparation of furnace charge, observe specified time of furnaces operation and maintain
proper automatic control. This solution also requires arrangements between the KGHM
PM S.A. Division and the Company "A" on both the work organisation and incurred costs.
That still does not guarantee that the problem will be successfully solved. Moreover, it
does not seem real to influence operations of an external company, even if the company
is linked through capital ties with KGHM PM S.A.
5.2 Maintaining the required level of power factor tgφ
Speaking about maintaining the required level of power factor tgφ it should be mentioned
that reactive power is compensated in the KGHM PM S.A. Division power network by means of
capacitor banks installed at the Main Transformer Station at the medium voltage side and in low
voltage switchgears or at individual LV loads. Since the Division does not exceed tgφ limit at the
point of connection to the utility distribution system, it does not incur additional fees for failure to
comply with requirements.
In the case of Companies "A", "B" or "C" power factor tgφ limits are exceeded, thus
reactive power compensation should be implemented.
In view of the above, for each of discussed cases there should be performed a detailed
cost analysis of installation of a capacitor bank or capacitor bank with reactive power controller.
It should be born in mind that, similarly to reactive power charges, the cost of capacitor bank
installation should be incurred by the consumer.
28
5.3 Summary and conclusions
The conclusions and findings are summarised in the table below to provide a clear
overview of proposed modifications.
Measurement at
the feed point:
Company "A"
Irregularities found
Recommended solution
Additional requirements
Exceeded Plt and tgφ
FC/TCR installation
Company "B"
Capacitor bank
installation
Company "C"
Capacitor bank
installation
- Portable network analyser
- Expansion of the Central
System for Electricity Balancing
and Settlement in order to
include power quality
parameters at 110kV feed
points
KGHM PM S.A.
Division
Exceeded Plt; capacitor
bank manual switching
Capacitor bank automatic
control
Table 9 Proposed solutions to detected irregularities
Investigation of the power network in one of KGHM PM S.A. divisions was carried out in
terms of electrical power quality at the supplier-customer level. This involves power quality
issues, particularly voltage fluctuations and occurrences of exceeding long-term flicker severity
Plt limit values. Detected anomalies allow handling the problems and, where possible,
implementing solutions improving the quality of power. Whether the costs of such solutions
should be born solely by customers (if they are the source of disturbances) or be shared with
KGHM PM S.A., is a separate matter. Implementation of electrical power quality improvements
may protect us in the future from unfavourable changes to contracts with utility companies or
from claims raised by our customers.
In order to get complete information on the quality of electrical power, both purchased and
sold, the existing Central System for Electricity Balancing and Settlement should be expanded to
include power quality parameters at 110kV feed points. Such data would enable in-depth
analysis of electric power parameters, particularly within a long time-frame.
The measurements should undoubtedly be continued not only at the points where
electricity is sold but also on the Division's departments, e.g. Electrorefining Section where
voltage fluctuations may adversely impact the electrolysis process. In order to take preventive
remedy measures it is worth knowing where, and to what extent, we are dealing with the poor
quality of electrical power. In such cases the use of a portable PQ analyser would be required.
The economic effects of modernization and modifications, that certainly require
substantial capital investment, will not be instantaneous and their impact is difficult to estimate.
Production process effectiveness and quality, equipment lifetime and work accidents rate are
influenced by many factors. Nevertheless improving even one of these factors may result in
considerable improvement in both human working conditions and equipment operation. A costsbenefits analysis of the planned investment should minimise the investment risk and ensure that
estimated effects will be close to real.
29
References
[1] –
Polish Standard PN-EN 50160: "Voltage characteristics of electricity supplied by public distribution
networks", 2010.
[2] –
K.Chmielowiec "Obróbka statystyczna wyników"; AGH-UST Krakow 2012
[3] –
K.Piątek "Sposoby redukcji wahań napięcia"; AGH-UST Krakow 2012
[4] –
Joint publication "Poradnik Inżyniera Elektryka" vol 3; Wydawnictwa Naukowo-Techniczne,
4th edition, Warsaw 2011;
[5] –
R.Strzelecki, G.Benysek "Układy STATCOM i ich rola w systemie elektroenergetycznym";
Uniwersytet Zielonogórski 2004;
[6] –
A.Firlit, W.Łoziak, J.Bielewicz "Rozproszony system monitorowania jakości dostawy energii elektrycznej w
sieci zasilającej AGH (RSM-JDEE) Power Quality Smart Metering"; AGH-UST, KrakOw 2011
[7] –
A. Wetula „Analiza wahań napięcia i uciążliwości migotania” AGH-UST Krakow 2012
[8] –
Z. Hanzelka "Automatyka - Elektryka - Zakłócenia nr 5/2011"; WWW.ELEKTRO-INNOWACJE.PL
[9] –
Energy Law Act of April 10, 1997 (uniform text Dz.U. [Journal of Laws] 2012, item 1059)
[10] –
Regulation of the Minister of Economy of May 4, 2007 on detailed conditions for the operation of the power
system (Dz.U. [Journal of Laws] No. 93, item 623 of May 29, 2007).
30

Electrical Power Quality Analysis of the KGHM

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