Relay protection notebook - Seng Ou
Assignment
+ Study one type of relay protection
- testing
- characteristics
- configurrations...
+ Setting always has 3 steps:
51 - 3-phase
50 - 3-phase
51 - 1-phase
50 - 1-phase
Legend
21: Distance protection
25: Sync-check relay
27: Under voltage relay
50BF: Breaker failure protection
50: Instantaneous phase overcurrent
50N: Instantaneous ground overcurrent
51: Time delay phase overcurrent (includes IDMT and Definite Time
Delay)
51N: Time delay ground overcurrent
51GB: Ground backup overcurrent
59: Overvoltage relay
67: Directional phase overcurrent
67N: Directional earth fault overcurrent
81: Frequency relay
87B: Bus Differential Protection
87T: Transformer Differential Protection
BCU: Bay control unit
DTT: Direct transfer trip
Direct Transfer Trip (DTT) is a teleprotection scheme that involves
sending trip signals from one location to another via a
telecommunications transport, such as a phone line, radio, or fiber optics.
21: Positive sequence impedance
22: Negative sequence impedance
20: Zero sequence impedance
CB: Circuit Breaker
PQ: Power Quality Meter
DMM: Digital Multi Meter
79: Auto Recloser
+ What is the different between Dropout time and Tripping time?
+ Short circuit problem
Relay setting
+ Overcurrent Relay
Phase A, B, C (50/51)
+ Earth Fault Relay
Phase to Earth (50/51N)
+ Under Frequency
81O/U
Diagram (Draw or Insert the picture)
+ Load shedding
120% of Transformer
Capacity Voltage Enable load shedding
TR1 50MVA 110%
+ Load shedding (cutting feeder)
Time 1 Time 2 Time 3
F4 F5 F6
CT ratio 1200-800-400:1
Note: 1200-800-400 (3 primary)
Note: 1 (secondary)
+ Calculate Setting
|I1+I2+I3+…+In|=0
I diff = |
I1+I2+I3+...
+In |
???? Irest=|I1|
I1 I2 I3 In +|I2|+|I3|+...+|
In|
+ The Minimum possible timer setting
t1: t1>t (CB) + t (Rest) + t (relay)
t2: t2>t (a) + t (CB) + t (Res) + t (relay)
Note: t (a): delay time
Le 12/02/2023
+ Characteristic of Earth Fault and Differential Relay
+ Tripping characteristic of the Differential Protection
Idiff/Iref
Characteristic for single-side
feed
m2
Isetting
Idiff> IR1, m2
Le 13/02/2023
office prepare for IR/Iref
+ Testing Relay P123 Iat(biased) GS4
- Load shedding
Note: Load shedding is a process to address situations when electrical
demand approaches or exceeds supply levels. In these situations, it is
sometimes necessary to temporarily interrupt the delivery of electricity to
maintain the integrity of the electric grid and to prevent catasrophic grid
failures and extended outages for customers.
Shedding load may be necessary if there is a shortage of electricity
supply or if power lines are at risk of being overloaded. Factors that can
necessitate load shedding include: extreme weather, sharply increased
electric demand, unplanned genration plant outages, transmission
constraints, damage to equipment, unavailability of purchased power, or a
combination of these condition.
Shedding load is always a last resort, but. When necessary, can
prevent prolonged power outages or extensive damage that could severely
affect the reliability of the power grid for weeks or even months.
Source: https://www.publicpower.org/system/files/documents/Electric-
System-Load-Shedding.pdf
+ Under voltage inverse time delay
t = [TMS / |1-V/Vs|]
Note: V: applied input voltage
Vs: relay setting voltage
Vs > V
+ Overvoltage
t = [TMS / |V/Vs|-1]
V > Vs
Le 22/02/2024
Need VT (undervoltage) (feeder)
+ P127 Undervoltage (function) GS1, GS2
- GS1: outgoing feeder
- GS2: outgoing feeder
- GS3: P127 (can); P123 (cannot)
P123 (cannot) -> VT -> config (change relay wiring)
+ 3 steps: 5s, 7s, 9s
+ Vrated < 10%
+ Completed set can be used for UV (under voltage)
XJ
P123 No.27 -> out -> Tn...
JSZ60???
P127
GS TR1 TR2 TR3 TR4
GS1 ok ok ok
GS6 Add Add ok
GS28✘
GS29✘
GS35✘
GS38 ✔
GS52 ✘
GS66
GS69
GS70-78
GS80-93
GS EDC
+ Set the relay setting (Can)
+ Understand the configuration (Can)
+ Analyze the fault
22kV Incoming Switchgear
+ SIEMENS
51 Set
- 110% of FLA (Full Load Amps)
- NI
- Coordinate time margin not less than 0.6s at Maximum 3-phase fault
50 Set
- 100% of FLA
- Operating time 0.5s
51N set
- 25% of FLA
- NI
- Not less than
