SLTC ELECTRICAL SYSTEMS TEST 2 QUESTIONS WITH VERIFIED SOLUTIONS LATEST UPDATE 2026
Substation - Answers An integral part of the power system, where the voltage is transformed from a
higher voltage to a lower voltage or the reverse using transformers
What does a typical substation contain? - Answers 1.) Termination structures
2.) High-voltage switchgear
3.) One or more power transformers
4.) Low voltage switchgear
5.) Surge protection
6.) Controls
7.) Grounding system
8.) Metering
How many basic purposes does a sunstation serve? - Answers Three
Substation purpose one - Answers Switching equipment and circuit in and out of the system- This is
accomplished by circuit breakers and associated protective relaying equipment and by isolating
devices, such as disconnect switches
Substation purpose two - Answers Voltage transformation- i.e. stepping up or stepping down voltages
in the system. This is accomplished by the main component of the substation - the transformer
Substation purpose three - Answers Voltage Control- This is accomplished by shunt reactors (mainly
on the high voltage system), shunt capacitors, voltage regulators, "load tap changing" transformers,
etc.
The ground grid is a critical element of the substation and is designed to provide the following
functions - Answers 1.) Provide a path to ground for lightning
2.) Provide a ground for all substation equipment
3.) Ensure the safety of working in the station by limiting the ground potential differences
4.) Ensure the safety of the public who may be near the fence during a fault condition
5.) Provide a ground source for all lines coming in and out of the substation
Environmential Considerations - Answers Apperance, sound, oil spill containment
Bus conductors - Answers The substation high and low voltage buses form the common collecting
point for receiving and redistributing the power.
Bus conductors are usually _____ and made of ________ - Answers Heavy, Aluminum
Varying Bus conductor shapes - Answers Flat bus "bars" and round conductors
Power transformers - Answers They can contain large amounts of mineral oil. Most new transformers
are single three-phase units and can be very large, requiring special transportation from the
manufacturer to the site.
Circuit breakers - Answers The breaker is designed to interrupt current under normal load conditions,
when current flow may be many times greater than normal. The breaker control system must be
designed to trip (i.e. open) the breaker quickly and automatically in the event of a fault. This is
accomplished by protective relays, which sense faults and send signals to the appropriate breaker to
trip.
Oil circuit breakers - Answers Oil filled breakers to provide cooling and to prevent arcing when the
switch is activated
SUlfer hexaflouride circuit breakers - Answers Breakers filled with compressed gas known as SF6. The
gas extinguishes the arc created by he current flow when the contacts are opened
Air circuit breakers - Answers Breakers filled with compressed air which is used to quench the arc
created by the current flow when the connection is broken
Vaccum circuit breakers - Answers A vaccum circuit breaker utilizes a vaccum of extremely low
pressure to extinguish arcing when the circuit breaker is opened and to act as a dielectric to insulate
the contacts after the arc is interrupted
Circuit switchers - Answers Circuit swithcers provide equipment protection for transformers, lines,
cables, and capacitor banks. They are also used to energize and de-energize capacitor banks and other
circuits
Disconnect switches - Answers used to redirect or cutoff power flows for load balancing or
sectionalizing so that you can isolate pieces of equipment for maintenance or testing. There are many
varieties used, some of which are capable interrupting load current and even ceryain levels of fault
current, and others which cannot be opened under load at all
Substation - Answers An integral part of the power system, where the voltage is transformed from a
higher voltage to a lower voltage or the reverse using transformers
What does a typical substation contain? - Answers 1.) Termination structures
2.) High-voltage switchgear
3.) One or more power transformers
4.) Low voltage switchgear
5.) Surge protection
6.) Controls
7.) Grounding system
8.) Metering
How many basic purposes does a sunstation serve? - Answers Three
Substation purpose one - Answers Switching equipment and circuit in and out of the system- This is
accomplished by circuit breakers and associated protective relaying equipment and by isolating
devices, such as disconnect switches
Substation purpose two - Answers Voltage transformation- i.e. stepping up or stepping down voltages
in the system. This is accomplished by the main component of the substation - the transformer
Substation purpose three - Answers Voltage Control- This is accomplished by shunt reactors (mainly
on the high voltage system), shunt capacitors, voltage regulators, "load tap changing" transformers,
etc.
The ground grid is a critical element of the substation and is designed to provide the following
functions - Answers 1.) Provide a path to ground for lightning
2.) Provide a ground for all substation equipment
3.) Ensure the safety of working in the station by limiting the ground potential differences
4.) Ensure the safety of the public who may be near the fence during a fault condition
5.) Provide a ground source for all lines coming in and out of the substation
Environmential Considerations - Answers Apperance, sound, oil spill containment
Bus conductors - Answers The substation high and low voltage buses form the common collecting
point for receiving and redistributing the power.
Bus conductors are usually _____ and made of ________ - Answers Heavy, Aluminum
Varying Bus conductor shapes - Answers Flat bus "bars" and round conductors
Power transformers - Answers They can contain large amounts of mineral oil. Most new transformers
are single three-phase units and can be very large, requiring special transportation from the
manufacturer to the site.
Circuit breakers - Answers The breaker is designed to interrupt current under normal load conditions,
when current flow may be many times greater than normal. The breaker control system must be
designed to trip (i.e. open) the breaker quickly and automatically in the event of a fault. This is
accomplished by protective relays, which sense faults and send signals to the appropriate breaker to
trip.
Oil circuit breakers - Answers Oil filled breakers to provide cooling and to prevent arcing when the
switch is activated
SUlfer hexaflouride circuit breakers - Answers Breakers filled with compressed gas known as SF6. The
gas extinguishes the arc created by he current flow when the contacts are opened
Air circuit breakers - Answers Breakers filled with compressed air which is used to quench the arc
created by the current flow when the connection is broken
Vaccum circuit breakers - Answers A vaccum circuit breaker utilizes a vaccum of extremely low
pressure to extinguish arcing when the circuit breaker is opened and to act as a dielectric to insulate
the contacts after the arc is interrupted
Circuit switchers - Answers Circuit swithcers provide equipment protection for transformers, lines,
cables, and capacitor banks. They are also used to energize and de-energize capacitor banks and other
circuits
Disconnect switches - Answers used to redirect or cutoff power flows for load balancing or
sectionalizing so that you can isolate pieces of equipment for maintenance or testing. There are many
varieties used, some of which are capable interrupting load current and even ceryain levels of fault
current, and others which cannot be opened under load at all
