PQ Data Applications in Con Edison

Transcription

1 PQ Data Applications in Con Edison John Foglio July 29th, 2014

2 Power Quality Monitoring System 69 PQ monitors currently installed in our secondary networks 2

3 Power Quality Monitoring System 135 PQ monitors installed in the 62 area substations TR #1 TR #2 TR #3 TR #4 TR #5 PQ PQView 3

4 Power Quality Data Applications Reactance-to-Fault (RTF) Fault locating Cut-in Open-Auto (CIOA) Inrush vs. Fault Distribution Fault Anticipation (DFA) Sub-cycle Faults Second Faults Faults caused by backfeed 4

5 RTF Single-Phase Fault I 0 = 2kA I 0 = 2kA Total Current I 0 = 4x2 ka = 8kA I 0 = 2kA I 0 = 8kA I A I 0 = 2kA V A Voltage Drop 5

6 RTF Fault Location Prediction Feeder Trips due to Fault PQ Meter Captures Voltage & Current PQView Calculates Reactance RTF Application Matches Reactance To Feeder Model Voltage (kv) Current (ka) Single-Phase Fault Evolves Single-Phase into Two-Phase Fault Evolves into Two-Phase Va Vb Vc Va Ia Vb Ib Vc IcIa Ib Ic XTF Voltage (kv) Current (ka) Reactance (ohms) B AB Time (s) Time (s) EPRI/Electrotek PQView Visual Fault Locator Display on VDIS 6

7 RTF Visual Electric Distribution Information System 7

8 How Accurate is RTF? 8

9 Cut-In Open-Auto (CIOA) Cut-In Open-Auto (CIOA) describes a feeder trip immediately upon re-energization A CIOA could be caused by a fault or by inrush current Relays at area substations detect an over-current condition on the feeder and trip the breaker If there is no fault, the feeder can be re-energized quickly 9

10 CIOA Fault vs. Inrush Current Bensonhurst 1 TR3-10/8/ :43: Bensonhurst 1 TR3-10/8/ :43: Va Vb Vc Ia Ib Ic Ires Volts g ( ) F A U L T Amps Time (s) Time (s) WATERST - 5/16/ :00: WATERST - 5/16/ :00: Volts Va Vb Vc I N R U S H Amps Ia Ib Ic Time (s) Time (s) 10

11 CIOA PQView Software 1. PQ Monitor captures an event. 2. PQView Software differentiates between inrush current and fault current. 3. notification of inrush event sent to distribution list. 11

12 Distribution Fault Anticipation (DFA) - Self Clearing Faults Typical Characteristics (Tojovic/Williams*) Self cleared within ½ cycle Always occur near a voltage peak Frequency of occurrence increases over time Most typically associated with mechanical and heat-shrink joint failures A conductive path to ground is established and then clears in ½ cycle, this could be due to water or impurities in the splice Not detectable by Electromechanical Relays Since PQNodes are installed at Transformer Secondary, they can t narrow down the affected feeder Can be detected by existing Microprocessor Relays with new settings 12

13 DFA - Case Study Data Available to Operators in Real Time SEAPORT2-9/22/ :00: Va Vb Vc Ia Ib Ic Voltage (V) No Operations Found 3000 Sub-cycle Fault (7200 Amps RMS) Operations Correlation (no breaker operation at substation) Current (A) Time (s) 13

14 DFA Advantages The relay is set to trip the feeder breaker for two subcycle events within 1000 seconds. Feeder Removed from Service under Controlled Conditions Low Energy Testing vs. High Energy In Service Fault Clearing Safety Reliability 14

15 What is a Second Fault? After a feeder is repaired an Ammeter Clear and Hi- Potential test are performed Between 9/1/2010 9/1/2013 we analyzed 179 FOTs in Manhattan, Brooklyn & Queens 9/1/2010 9/1/2013 Brooklyn Queens Total FOTs analyzed Failed ammeter clear Failed on the rise Failed at test voltage 7 4 FOTs that failed on rise or ammeter clear 94% 94% 15

16 Second Fault Single Line-to-Ground Fault Analysis Part 1 Power Transformer Primary Feeders Secondary Network C C C C A B C 16

17 Second Fault Single Line-to-Ground Fault Analysis Part 2 Power Transformer Primary Feeders Secondary Network C C C T A B C There is an overvoltage on the unfaulted phases that can be up to line-to-line voltage This may cause a 2 nd fault! 17

18 Second Fault Single Line-to-Ground Fault Analysis Part 3 Power Transformer Primary Feeders Secondary Network C C C T A B C 18

19 Second Fault Detection Program Project Goal Develop methods to detect the presence or absence of a second fault on primary feeders during feeder OAs using Power Quality Data Monitors. Detection Methods Negative Sequence/ Current Unbalance Substation PQ monitor captures an increase in negative sequence current without zero sequence current shortly after the initial fault Second Voltage Dip Network PQ monitor captures an additional voltage dip shortly after the initial fault 19

20 Second Fault Initial Fault at the Substation Zero Seq / Ground Current Negative Seq / Current Unbalance Rise in current with a dip in voltage Causes feeder to OA 20

21 Second Fault Subsequent Event at Substation Subsequent Event Zero Seq / Ground Current Negative Seq / Current Unbalance A Negative Sequence Current Filter installed on the monitor triggers when a current unbalance is detected to capture the event. The presence of negative sequence current without zero sequence current indicates current is passing thru a network transformer to a second fault. 21

22 Second Fault Subsequent Event at the Network Subsequent Network Voltage Dip Method uses existing network monitors with no new equipment needed First voltage dip occurs during initial fault Second voltage dip occurs shortly after the initial voltage sag Verify no additional feeders OA Initial Event Subsequent Event 22

23 Second Fault PQ Monitor with Negative Sequence Filter Currently 51 Negative Sequence Current Filters have been installed: Region Installed Remaining Manhattan 23 3 Brooklyn 6 0 Queens 7 0 Bronx 2 4 Westchester 11 1 Staten Island 2 3 Voltage Module Current Module PQ Monitor Negative Sequence Filter 23

24 Second Fault Negative Sequence Current Filter A, B, and C phase currents input into the filter. Filter generates an output based on the negative sequence component of the current. I A I B I C NSCF I 2 Triggers monitor to capture event when negative sequence current passes a threshold. Enables monitor to capture events that are not triggered by voltage fluctuations. 24

25 Second Fault Negative Sequence Notification PQView sends an notification after capturing a negativesequence overcurrent without any operation Subject: Fault Notification: Plymouth ST TR4 Subject: Negative-Sequence Overcurrent Event with No Operations: Plymouth ST TR4 No Operations 25

26 Second Fault Manhattan - Accuracy Predicting No Second Fault 100.0% 100.0% 100.0% % 84.6% 92.3% 73.7% 83.3% 76.3% 82.6% 86.7% 95.5% 90.0% 80.0% 77.8% 70.0% % 60.0% % 40.0% % 20.0% % 0 Jun-13 Jul-13 Aug-13 Sep-13 Oct-13 Nov-13 Dec-13 Jan-14 Feb-14 Mar-14 Apr-14 May-14 Jun-14 Predicted no FOT Feeder did not FOT Accuracy %

27 12 Second Fault Manhattan - Accuracy Predicting A Second Fault 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% 100.0% 90.0% % 70.0% % % 40.0% % % 10.0% 0 Jun-13 Jul-13 Aug-13 Sep-13 Oct-13 Nov-13 Dec-13 Jan-14 Feb-14 Mar-14 Apr-14 May-14 Jun-14 Predicted FOT Feeder FOTed Accuracy %

28 Improving the Accuracy of Detecting a Second Fault Upgrade firmware to enable existing monitors to trigger on a change in negative sequence Have field crews identify and report back the faulted phase(s) found Examine ways a second fault may develop after the feeder is dead-on-backfeed such as through capacitor discharge or a manhole fire 28

29 Thank you! Questions / Comments? 29