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WorksheetsCircuit Breaker and Protection Relay
Total questions: 40
Worksheet time: 31mins
The type of MCB used for residential loads
Type B
Type C
Type A
Type D
The type of MCB used for motor loads.
Type B
Type C
Type A
Type D
Type D MCB can withstand inrush current up to 20x.
TRUE
FALSE
The unit of electric current
Amperes
Volts
Ohms
Watts
The circuit breaker will protect all of the following, EXCEPT ONE:
Overload
Short Circuit
Ground Fault
Overvoltage
The zone covered by A is called ___________.
Thermal Release
Magnetic release
Earth Fault
Electronic Fault
A situation where the system draws more electricity than a circuit can safely handle.
short circuit
overload
overvoltage
ground fault
The unintentional connection between two live cables.
short circuit
overload
overvoltage
ground fault
A type of circuit breaker that uses gas to suppress electric arc.
SF6
Oil Circuit Breaker
Vaccum
Air Blast
An RCD will trip when the amount of current ENTERING is _____________ the amount of RETURNING current
less than
more than
equal to
more then less
An ____________ relay is one in which no intentional time delay is provided.
instantaneous
inverse time
electronic
RCD
The ___________ circuit breaker allows only one power source to be on at one time, although both can be off at the same time.
SF6
Interlock
RCS
overload relay
The Vacuum Circuit Breaker is practical to use above 38 kV.
TRUE
FALSE
The SF6 is an electro-negative gas and has a strong tendency to absorb free electrons.
TRUE
FALSE
The Vacuum Circuit Breaker contain exhaust of gasses to the atmosphere.
TRUE
FALSE
(a) is an electrical breakdown of a gas that produces a prolonged electrical discharge
The suppression of an ARC can be delayed.
TRUE
FALSE
This MCB is type _______.
A
B
C
D
This circuit breaker has interrupting rating of (a) Amperes.
How many poles does this circuit breaker has?
(a)
This circuit breaker is next to MCB which is typically used for system current range from 100 A – 2,500 A.
Molded Case
Vacuum
SF6
Air Blast
Normally, the circuit breaker can detect frequency issues.
TRUE
FALSE
The time current curve of Air Circuit breaker can be adjusted.
TRUE
FALSE
The smallest amount of current that an RCD can detect is (a) mili-Ampere.
According to Saudi Building Code, the low voltage circuit breaker need to open before (a) seconds to protect the circuit.
The zone covered by "B" is called _____________.
Thermal release
magnetic release
electronic release
RCD release
The temperature of an electric arc can reach as high as ___________ degree celcius.
10,000
15,000
20,000
5,000
The SF6 circuit breaker can absorb free electrons.
TRUE
FALSE
The VCB is practical to use for voltages below 38 kV.
TRUE
FALSE
An electric circuit has a supply voltage of 440 Volts and resistance of 5 ohms. The value of electric current is (a) Amperes.
What is the device number of Phase reversal caused by negative sequence current?
21
87
51
46
A separate relay detecting voltage across the neutral grounding circuit which typically provided for sensitive detection of a stator ground fault.
Stator Ground Fault Protection
Rotor Ground Fault Protection
Overvoltage
Undervoltage
Detects loss of excitation (or loss of field) that will result in a loss of synchronism.
Device number 41
Device number 40
Device number 51
Device number 50
Device number 32 offers _________ protection.
motoring
ground fault
stator ground
loss of field
This device will trip the circuit breaker when the frequency of the generator is beyond the operating range.
82
81
75
73
The CT ratio is 200:5. What is the secondary current when the CT primary has 50 Amperes? (answer number only without unit)
(a)
_____________ is essentially an ohmmeter and operates whenever the impedance of the protected zone falls below a pre-determined value.
Distance relay
differential relay
frequency relay
Undervoltage relay
All of the circuit breaker below protects transformer B, EXCEPT:
Circuit Breaker 1
Circuit Breaker 2
Circuit Breaker 3
Circuit Breaker 4
Which circuit which SELECTIVITY is applied?
Circuit A
Circuit B
Both A and B
No selectivity applied in both circuits
The relaying system should be simple so that it can be easily maintained.
TRUE
FALSE
