Power System Protection. Dr. Lionel R. Orama Exclusa, PE Week 9

Transcription

1 Power System Protection Dr. Lionel R. Orama Exclusa, PE Week 9

2 Pilot Relaying Communication channels & signals Pilot wire schemes Opposed voltage Circulating current Blocking schemes Directional comparison Phase comparison Tripping schemes DUTT, PUTT, POTT Hybrid schemes Copyright L.R. Orama

3 Suggested Reading Mason Chapter 5, pgs Chapter 6, pgs Copyright L.R. Orama

4 Pilot Relaying Zone 1- under-reach For F2, R1 send signal to R2 to open No intentional time delay, Op time for signal to get to the remote station Copyright L.R. Orama

5 Blocking & Tripping Schemes Blocking Schemes When a signal is received from remote terminal, tripping is not permitted (blocked) at local terminal Tripping Schemes When a signal is received from a remote terminal, tripping occurs at local terminal Copyright L.R. Orama

6 Blocking & Tripping Schemes Fault Internal External Scheme Tripping Blocking Tripping Blocking Signal Signal sent Signal not sent Signal not sent Signal sent Copyright L.R. Orama

7 Blocking & Tripping Schemes Channel failure Blocking (security) Internal fault not a problem External fault, signal not sent problems Tripping (dependability) Internal fault, signal not sent problems External fault - not a problem Copyright L.R. Orama

8 Channels & Signals for Pilot Relaying Types of Channels for line protection Wire lines & cables Fiber optic cables Power line carrier Microwave Copyright L.R. Orama

9 Wire lines (Pilot Wire) Wire line twisted pair of wires between terminals Usually telephone circuit is rented Open wire or buried cable Can be used as channel for: AC pilot relay, up to 10 miles Frequency shift audio tone signal ( Hz), up to 30 miles Copyright L.R. Orama

10 Wire Line & Cables Advantages Simple Economical for short distances Disadvantages Susceptible a natural hazards (lightning) Susceptible to electromagnetic interference, EMI (noise) Copyright L.R. Orama

11 Fiber Optic Cable Glass rather that conductor Advantages Immune to EMI (noise) Limitations Expensive Special termination equipment Copyright L.R. Orama

12 Copyright L.R. Orama

13 Power Line Carrier Advantages Most reliable form of communication Most economical for few channels over long distance Repeaters not require for long distance Disadvantages Susceptible to line noise and fault attenuation Limited frequency spectrum Copyright L.R. Orama

14 Microwave Copyright L.R. Orama

15 Microwave Advantages Independent path not affected by line noise or faults Accommodates a large number of channels Large frequency spectrum available Disadvantages Very expensive for low channel density Interim sites required for repeaters Subject to propagation fades Copyright L.R. Orama

16 Pilot Relaying Schemes Pilot wire schemes Blocking schemes When signal is received from remote terminal, tripping is not permitted at local terminal Tripping schemes When signal is received from remote terminal, tripping occurs at local terminal Copyright L.R. Orama

17 Pilot Wire Schemes Opposed voltage Circulating current Basically current differential schemes Application considerations Loop R < 2000 Ohms Shunt C < 1.5uF (20-30 miles) Copyright L.R. Orama

18 Opposed Voltage AC Pilot Wire Scheme External Fault Copyright L.R. Orama

19 Opposed Voltage AC Pilot Wire Scheme Internal Fault Copyright L.R. Orama

20 Opposed Voltage AC Pilot Wire Scheme Open Pilot Wire Copyright L.R. Orama

21 Opposed Voltage AC Pilot Wire Scheme Short Circuited Pilot Wire Copyright L.R. Orama

22 Circulating Current AC Pilot Wire Scheme External Fault Copyright L.R. Orama

23 Circulating Current AC Pilot Wire Scheme Internal Fault Copyright L.R. Orama

24 Circulating Current AC Pilot Wire Scheme Open Pilot Wire Copyright L.R. Orama

25 Circulating Current AC Pilot Wire Scheme Short Circuited Wire Copyright L.R. Orama

26 Comparison of Failure Modes Copyright L.R. Orama