1
Q
3
A
Interlocking relay
2
Q
12
A
Over-speed
3
Q
14
A
Under-speed
4
Q
20
A
Electrically operated valve
5
Q
21
A
Distance relay
6
Q
26
A
Apparatus thermal device
7
Q
27
A
Undervoltage relay
8
Q
33
A
Position switch
9
Q
38
A
Bearing protective
10
Q
40
A
Field Relay
11
Q
41
A
Field circuit breaker
12
Q
43
A
Manual transfer or selector device
13
Q
46
A
Reverse-phase, or phase-balance, current relay
14
Q
48
A
Incomplete sequence relay
15
Q
49
A
machine, or transformer thermal relay
16
Q
50
A
Instantaneous overcurrent relay
17
Q
51
A
AC time overcurrent relay
18
Q
52
A
AC circuit breaker
19
Q
55
A
Power factor relay
20
Q
59
A
Overvoltage relay
21
Q
63
A
Pressure switch
22
Q
64
A
Ground protective relay
23
Q
70
A
Rheostat
24
Q
72
A
DC circuit breaker
25
80
Flow switch
26
81
Frequency Relay
27
86
Locking-out relay
28
87
Differential protective relay
29
94
trip-free relay
30
Protective relays have been described as the _____ of the system
Watchdogs
31
Auxiliary relay
operates in response to the opening or closing of its circuit to assist another relay or device
32
Verification relay
verify power system conditions and permit automatic functions other than opening a circuit breaker during fault conditions.
33
The most common fault characteristics
1. increased current in one or more phases flowing towards the fault (2 to 20 times normal load current)
2. reduced voltage in one or more phases ( voltage will be lowest at the fault)
3. Fault power always flows toward the fault
4. Temp rise in electrical equipment.
34
Relays operate on two fundamentally different operating principles
1. electromagnetic attraction
| 2. electromagnetic induction
35
A contact that is open when the relay is de-energized is termed an open or ___ contact and a contact that is closed when the relay is de-energized is termed a closed or a ___ contact
a
b
36
High speed relays operate in ____ cycles or less while slow speed relays operating time _____
3
exceed 3 cycles
37
Differential relays protect against ____
internal faults
38
59n (ground fault overvoltage relay)
current in the neutral transformer produces a voltage in the secondary which operates the relay if the voltage exceeds a predetermined level
39
For pumping units where inrush amps are high, what is it desirable to provide
a relay (51v) which will properly protect the unit against overloads caused by a fault while preventing a trip on starting amps
40
What are four major faults effect power systems
1. Three phase
2. Line to line ( two phase) or Phase to phase
3. double line to ground
4. single line to ground (phase to ground)
41
____ relaying is the first line of defense or protection against electrical or mechanical trouble
Primary
42
_______ relaying functions only when primary relaying fails
"back-up"
43
relays that empoly the electromagnetic induction principle provide a ______, which can be adjusted on some, by changing the distance the moving contact must travel
time - delayed operation
44
What are a RTD and where are they located?
Resistance Temperature Detectors
located in the critical temp areas of the apparatus being protected to provide either an alarm or a direct trip action.
45
what is ICS
indicating contactor switch
46
sealed in
prevents arcing
shunt in parallel with the relays main contacts
keeps contacts closed until reset
47
An inverse-time curve is
the operating time becomes less as the magnitude of the actuating quantiy is increased
48
what is the most common fault
phase to ground
49
time delay is obtained by
adjusting the travel distance of the contacts
50
distance relays use what to detect faults
impedance
Protective Relaying
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