Protective Relaying for DER

Transcription

1 Protective Relaying for DER Rogerio Scharlach Schweitzer Engineering Laboratories, Inc. Basking Ridge, NJ

2 Overview IEEE 1547 general requirements to be met at point of common coupling (PCC) Distributed resource (DR) response to area electric power system (EPS) abnormal conditions

3 Overview Distributed generation (DG) impact on distribution feeders Real Life Operation of DR Interconnection Protection Introduction to Symmetrical Components

4 IEEE 1547 General Requirements to Be Met at PCC Voltage regulation Integration with area EPS grounding Synchronization Inadvertent energization of area EPS Monitoring provisions Isolation devices Interconnection integrity

5 DR Response to Area EPS Abnormal Conditions Faults Reclosing Voltage excursions Frequency excursions Loss of synchronism Reconnection to area EPS

6 DR Response to Area EPS Faults DR unit shall cease to energize area EPS for faults on area EPS circuit to which it is connected

7 DR Response to Area EPS Reclosing DR shall cease to energize area EPS circuit to which it is connected prior to reclosing by area EPS

8 DR Response to Voltage Excursions Voltage parameters are to be met at PCC Interconnection system responds to rms or fundamental voltage Phase to phase Phase to neutral Voltage Range (% of base voltage) Clearing Time (s) V < V V V

9 DR Response to Frequency Excursions DR shall cease to energize area EPS when system frequency is in particular range DR Size Frequency Range (Hz) Clearing Time (s) 30 kw > 30 kw > < > < 59.8 to 57.0 (adjustable) 0.16 to 300 (adjustable) <

10 DR Response to Loss of Synchronism In this case, DR response Applies only to synchronous generators Is primarily a risk to generators Standard addresses this condition as being of concern only if it results in voltage fluctuations that violate flicker limitations

11 DR Reconnection to Area EPS Reconnection is delayed up to 5 minutes after area EPS steady-state voltage and frequency are restored Ranges include Frequency 59.3 to 60.5 Hz Voltage see ANSI C , Table 1

12 Power Quality Limitation to dc injection Limitation of flicker induced by DR Harmonics

13 Islanding Unintentional Intentional

14 DG Impact on Distribution Feeders Increased fault duty Unintentional islanding Relay desensitization Nuisance tripping Automatic reclosing Voltage regulation and flicker Ferroresonance

15 Increased Fault Duty Is caused by addition of generating sources and rotating machinery of considerable size Affects capability of equipment to carry and interrupt fault currents Requires both local and area EPS equipment ratings to be reevaluated

16 Unintentional Islanding Occurs when portion of area EPS and DR become electrically isolated from rest of area EPS and DR continues to energize island Should be avoided for two major reasons There is potential for negative effects on voltage, frequency, and power quality Islanded generator complicates both automatic reclosing and manual switching

17 Relay Desensitization Available short-circuit current increases with addition of DR Short-circuit current splits between substation and DR Substation short-circuit contribution can be significantly reduced when compared with value before addition of DR

18 Relay Desensitization Fault Current Distribution Without DR Substation R1 R2 Three-Phase 3I A 198 A F1

19 Relay Desensitization Fault Current Distribution With DR Substation R1 R DR Substation Three-Phase 3I A 24 A DR 399 Three-Phase 3I A 246 A F1

20 Nuisance Tripping Without DR F2 Substation R1 R2 Three-Phase 3I A 616 A

21 Nuisance Tripping With DR Substation R F2 R DR Substation Three-Phase 3I A 616 A DR Three-Phase 3I 0 3E A 0 A pu 3E 0

22 Operation for Fault in Adjacent Zone I SYS + I FAULT SYS 1 I SYS I FAULT 2 3 I FAULT DR

23 Automatic Reclosing DR should be disconnected before open interval expires By interconnection protection (81U, 81O, 59, 27) By DTT Minimum open or dead time to allow arc deionization and to avoid restrike is

24 Automatic Reclosing If DR can form sustainable island when separated from system, restoration becomes issue Utility feeder breaker has to be equipped with synchronism-check element and / or live-bus and dead-line logic OR combination of both elements works as permissive for reclosing utility feeder breaker

25 Automatic Reclosing Close Permissives Utility Bus Feeder and bus are in synchronism Utility bus is hot and line is dead DR 3 C T 3 Live Bus / Dead Line or Synchronism 1 Temporary Fault Multifunction Relay

26 PV Array Real Life Operation of DR Interconnection Protection Isolation Transformer 380 Vac 13,800 Vac Neutral Grounding Reactor 51P 51G Pole-mounted Recloser T C I VY VZ G 27 Recloser Control Overhead Distribution Feeder Ø-G Fault Simplified Single-Line Diagram

27 Recloser Control Simplified Trip Logic OR G 51P 51G OR OR TRIP RECLOSER

28 Relay Settings Element Setting Delay Description % ms Definite time undervoltage level % s Definite time undervoltage level % 950 ms Definite time overvoltage level % ms Definite time overvoltage level Hz ms (@ 57 Hz) Definite time underfrequency level Hz s (@ 58.5 Hz) Definite time underfrequency level Hz ms (@ 60.5 Hz) Definite time overfrequency 59G 8,200 V 1.33 s Definite time residual ground overvoltage 51P 60 A NA Inverse time phase overcurrent 51G 19.8 A NA Inverse time residual ground overcurrent

29 Relay Underfrequency Settings

30 Feeder Fault (C-Ground)

31 Undervoltage Element Pickup Time ms

32 Undervoltage Element Time Delay ms

33 Recloser Interruption Time ms

34 ms Total Clearing Time

35 Introduction to Symmetrical Components The solution of balanced multi-phase systems can be accomplished using singlephase methods The method of symmetrical components allows unbalanced multi-phase systems to be solved using single-phase methods. Introduced in 1918 by C.L. Fortescue

36 Insight it is shown that unbalanced problems can be solved by the resolution of the currents and voltages into certain symmetrical relations. When the constants are symmetrical, that is, when the system viewed from any phase is similar, then the symmetrical components of currents do not react upon each other so that it becomes possible to eliminate the mutual relations with their attendant complication in the solution of the problems. C.L. Fortescue

37 Decomposition of an Unbalancedd System

38 Symmetrical Components as a Function of Phase Quantities

39 Phase Quantities as a Function of Symmetrical Components

40 Phase-to-Ground Fault Two-Terminal System

41 Zero Sequence Network During the Fault + - N 0 ΔV 0 = I 0R * (3 x Z N + Z 0TR ) Z 0S I 0DR = 0 Z 0DR 3 x Z N I 0S 0 V 0Z X H 0 Z 0TR ΔV 0 CB CLOSED I 0S + I 0R R CLOSED V 0Z before trip = 2400 V < 2,735 V (pick up) V 0Z after trip = 3200 V > 2,735 V (pick up) H

42 Residual Ground Overvoltage

43 Sample DER Interconnected Through PV Array a Delta/ Wye Transformer Isolation Transformer Pole-mounted Recloser T C I VY VZ Overhead Distribution Feeder Ø-G Fault 51P G 59G Recloser Control Simplified Single-Line Diagram

44 E What is the 3V0 at the Recloser Location After Utility Separation? Z 1S I 1S = 0 CB OPEN Z 2S I 2S = 0 CB OPEN Z 0S I 0S = 0 Z 1L Z 2L V 1 V 2 V 0 R CLOSED R CLOSED I 1DR = 0 I 2DR = 0 Z 0DR X Z 1DR Z 1TR Z 2DR Z 2TR I 0DR = 0 H 0 Z0TR H CB OPEN Z 0L R CLOSED I 0R = 0

45 Conclusions There are several requirements to be met by DR at PCC location DR has to respond to abnormal conditions of area EPS Addition of DR to distribution feeder affects its protection, voltage regulation, fault duty, reclosing scheme, and so on

46 Conclusions Event report analysis is a great tool to validate DER interconnection protection settings Unbalanced phasors can be broken down into their symmetrical components Symmetrical components allow the use of simple single-phase calculations for analysis of unbalanced systems The resultant symmetrical components can be recombined into the phase components

47 Questions?

48 Questions to the audience Please provide 3 examples of DR impacts on distribution feeders. Please provide 3 examples of area EPS abnormal conditions that the DR has to respond to. Can a DR immediately reconnect following a successful feeder restoration? If not, how long is the qualifying time delay? What are the quantities monitored during the qualifying time delay?

49 Questions to the audience According to the theory of Symmetrical Components, an unbalanced set of currents can be decomposed in three other components. What are these components? How are the sequence networks interconnected to represent a phase-toground fault?