INTRODUCTION This document represents the relay settings for 10 MW GridTied SPV Plant at Charanka(GJ)
2.0
OBJECTIVE The Relay setting and Coordination analysis is conducted to recommend the relay settings and achieve proper coordination between relays installed at 10MW Solar Plant.
A. The Relay coordination study is performed to determine various relay settings under
normal operating condition and to ensure: a. Sensitivity to over current and earth faults under minimum and maximum fault conditions. b. Selectivity of relays. c. Stability for non operating conditions.
3.0
REFERENCE DRAWINGS/DOCUMENTS
a) 66kV Feeder C&R Panel, b) 66kV Transformer Bay C&R Panel,
4.0
SYSTEM DESCRIPTION The power distribution diagram is shown in the Single Line Diagram. As shown, 11kV voltage is generated through inverter transformer which is further stepped up to 66 kv and fed to grid.
5.0
STUDY APPROACH / BA SIS & A SSUMPTIONS The phase Fault level on 66kV bus is 10kA. Grading margin of 0.25 seconds has been considered between outgoing and incomer feeders. Back-up protection for O/C and E/F has been considered upto two levels only. Time of operation for Normal Inverse relay at 1.0 TMS (as per IEC) α
t = β / [(I/Is) - 1] Where, t = Tripping Time I = Fault current Is = Inverse time over current pickup, TMS = Time Multiplier Setting I/Is = Plug setting Multiplier = PSM α = 0.02, β = 0.14 α = 1, β = 13.5 α = 2, β = 80
For Normal Inverse For Very Inverse For Extremely Inverse
10 MW Grid Tied SPV Plant at Charanka(GJ).
6.0
RELAY IDENTIFICATION TABL E SN 1 2 3 4 5 6
7.0
RELAY NO. 50 50N 51 51N 67 87
DESCRIPTION Instantaneous Over current Instantaneous Earth fault IDMT Over current IDMT Earth fault Directional Over current Transformer Differential Protection
REMARKS
ATTACHMENTS Attachment-1:
Summary of Relay settings
Attachment-2:
Overcurrent and Earth fault Relay Co-ordination curves
Project : 10 MW Grid Tied SPV Plant at Charanka(GJ)
Project : 10 MW Grid Tied SPV Plant at Charanka(GJ)
ATTACHMENT‐2.2
Sheet 2 of 2
EARTH FAUL T CURRENT CURVES
100000 6 MVA TRAFO PRI 66kV LINE RMU I/C 11 KV INCOMER
10000
11 KV OUTGOING
1000
100
TIME(SEC)
10
1
0.1
0.01 1
10
100 If(A)
1000
10000
Project : 10 MW Grid Tied SPV Plant at Charanka(GJ)
ATTACHMENT 3 CALCULATION
Sheet 1 of 2
66KV OUTGOING LINE Setting Range
=
CT Ratio
=
Load Current
=
300.0 A
300 / 1A
Fault Current
=
Current Setting
=
10.00 kA 80 %
Relay Characteristics
=
Normal Inverse
IDMT O/C Relay settin g Multiples of plug setting current
=
10000
=
41.67
=
2.27 sec
=
0.05 sec
=
0.300 sec
=
0.13
=
0.29 sec
=
222.22
=
2.27 sec
=
0.05 sec
=
0.30 sec
=
0.132
=
0.29 sec
300 x 0.80 Relay opert'n time@
41.67
times PS and 1.0 TMS
Operating time of downstream O/C relay
t
β =
( PSM ) α
−
1
Allowing a grade margin of 250 msec, Operating time required TMS
=
0.30 sec 2.27 sec 2.27 x 0.13
Actual Opert'n time = Recommended Settings : Current Setting
=
80%
TMS
=
0.13
IDMT E/F Relay settin g Multiples of plug setting current
=
10000 300 x 0.15
Relay opert'n time@
222.22
times PS and 1.0 TMS
Operating time of downstream E/F relay (To Trafo feeder) Allowing a grade margin of 250 msec, Operating time required TMS
=
0.30 sec 2.3 sec
Actual Opert'n time = Recommended Settings :
2.27 x 0.130
Current Setting
=
15%
TMS
=
0.13
t
β =
( PSM ) α
−
1
Project : 10 MW Grid Tied SPV Plant at Charanka(GJ)
ATTACHMENT 3 CALCULATION
O/G to 6.0MVA TRANSFORMER Relay, Make Setting Range CT Ratio Load Current Fault Current Current Setting Relay Characteristics
= = = = = = =
Sheet 2 of 2
SIEMEN'S 7SR1103 0.1 to 40 In 60 / 1A 52.5 A 0.62 kA 110 % Normal Inverse
IDMT Relay sett ing (51) Fault current at the secondary side of 66/11kV, 6000 kVA transformer = (Considering Z = 8.5% for 6000 KVA Transformer)
3.71
Reflected current on primary side = (66 kV) = Multiples of plug setting current
618 A
=
618 60 x 1.10
Relay opert'n time@
9.36
times PS and 1.0 TMS
Operating time of downstream O/C relay Allowing a grade margin of 250 msec, Operating time required TMS
=
0.80 sec 3.06 sec 3.06 x 0.26
Actual Opert'n time =
kA
Recommended Settings : Current Setting TMS
= =
110% 0.26
Highset Setting (50) Relay Setting range Time delay
= =
0.1 to 40 In 0-150 sec
The relay has to trip for a fault in the primary side of Trafo i.e @
=
9.36
=
3.06 sec
=
0.55 sec
=
0.80 sec
=
0.26
=
0.80
0.741 kA
Multiples of plug setting current
=
0.741 60 x 1.00
Recommended Settings : Current Setting
=
1300%
Time Delay (DT)
=
0.05 sec
E/F Relay Setting (50N) Relay Setting range
=
Time delay
=
Current setting Time Delay (DT)
=
20%
=
0.05 sec
β =
( PSM ) α
−
10.00 kA
The relay shall be set such that it does not operate for the reflected down stream fault of 66kV side The minimum fault current for the relay to operate (Considering 20% margin) = 0.6175 x 1.2 times = =
t
0 to 64 sec
The relay has to operate with minimum time delay for ground fault in the primary side of Transformer
