Substation Basics Flashcards
What is a substation?
A station that houses equipment for switching, protecting and managing the flow of electricity.
What can a substation do?
Switch or re-route the flow of electricity from damaged circuits.
List some equipment you can find in a substation?
- Circuit Breakers
- Transformers
- Relays
- Disconnects
What are two types of substations?
Manned and unmanned
What does TSO stand for?
Transmission Substation Operator
Where is the TSO located?
Substation of Jurisdiction
What are TSOs responsible for?
All the substations and transmission lines in his or her area.
What are the functions of Substations?
- Switching
- Voltage Transformation
- Reactive Power Compensation
What is Switching?
Connecting or disconnecting lines or equipment from the system.
What is Voltage Transformation?
Power transformers are used to step voltage up and down to higher and lower values more suited to the needs of the system and the customers.
What is Reactive Power Compensation?
Shunt reactors, shunt or series capacitors, and synchronous condensers are used to control voltage by adjusting the reactive power (VARs) on the system.
In addition to standard functions, what else are substations designed to accommodate?
Control panels, relay protection for lines and equipment, alarms and AC and DC systems.
What is installed beneath the substation and what is it used for?
A grounding grid acts as the grounding medium for all substation structures.
What are the 3 key substation personnel?
SOS, TSO and SO
What is the SOS?
Substation Operator Supervisor is in charge of the operations at his or her Switching Center, and all substations under the SOS’s jurisdiction.
What is the TSO in charge of?
All real time operations at the Switching Center all other substations under his or her jurisdiction.
What are the duties of a TSO?
Writing down and approving switching programs, responding to unscheduled outages, coordinating with the Grid Control Center (GCC), coordinating with Distribution Operations Centers, and coordinating with other TSOs.
What is an SO and what do they do?
Substation Operator assists in the operation of the various substations to which he or she is assigned.
What are the duties of an SO?
- Station Inspections
- Routine Switching
- Emergency Switching
- Logging
- Reporting
List some Switching Equipment
- Circuit Breakers
- Circuit Switchers
- Disconnects
- Fused Disconnects
What do Circuit Breakers do?
- Connect or disconnect circuits or equipment from the power system.
- Rapidly isolate faulted portions of the power system
- Carry out routine switching operations, such as disconnecting a device to perform maintenance.
What is the primary function of a Circuit Breaker?
To interrupt current flow under load or fault conditions.
What are the 4 types of Circuit Breakers?
- Oil
- Air
- Gas
- Vacuum
How do Oil Circuit Breakers work?
Insulating oil extinguishes the arc
How do Air Circuit Breakers work?
Air extinguishes the arc
How do Gas Circuit Breakers work?
SF6 gas is used to extinguish the arc
How do Vacuum Circuit Breakers work?
A vacuum chamber prevents an arc from occurring since there are no air molecules to ionize. (These are used for lower voltage circuit breakers).
What are the different types of Circuit Breaker Operating Mechanisms?
- Spring
- Pneumatic
- Hydraulic
- Solenoid
What is a Circuit Switch?
- Cross between a Circuit Breaker and a disconnect
- Type of switch that, because of its interrupting capability, is considered to be a type of Circuit Breaker.
What is a Circuit Switch primarily used for?
Switching Capacitors and Reactors.
What is in the interrupting chamber of a Circuit Switch and what does it do?
SF6 Gas allows normal load current to be interrupted
What can some disconnects do?
Interrupt normal load current, others cannot. Some can only interrupt magnetizing current of unloaded lines and equipment.
What are disconnects not designed to do?
Interrupt fault currents
What are isolating disconnects with cat whiskers designed to do?
Allows the disconnect to interrupt magnetizing current, but not load current.
What are isolating disconnects with load break devices designed to do?
Interrupt load current (but still not fault current)
Where can you find isolating disconnects with load break devices?
Between back-to-back transformer banks in order to break parallel.
Where can you find isolating disconnects with cat whiskers?
On the high-side of transformers and sometimes on the low-side.
Disconnects that are used for isolating equipment have no means of what?
Current interruption
What does gang operated mean?
All three phases operate together.
What voltage are Gang Operated Disconnects most commonly found?
66kV and above
What are MODs?
Motor-Operated Disconnects
What are fused disconnects used for?
Protect Station Light and power transformer banks, “B” Banks and distribution capacitors from overheating due to heavy instantaneous fault currents or continuous overcurrents. Also act as a disconnect switch for isolating devices.
What are Power Transformers used for?
Devices used in AC Power Systems to convert electrical power from one voltage and current value into electrical power at some other voltage and current value.
How are SCE power transformers categorized?
By their voltage levels and/or applications.
What are the four different names of banks?
“AA”
“A”
“B”
“C”
What are AA Banks?
Both the high-side and low-side voltages are at the transmission levels. Thus all 500/220kV transformers are all “AA” Banks.
What is the primary side of a transformer?
“Input” side
What is the secondary side of a transformer?
“Output” side
What are A Banks?
The links between the transmission and subtransmission systems.
What are the Secondary voltages in an A Bank?
66kV and 115kV
What are “B” Banks?
Links between the subtransmission and distribution systems.
What are the secondary voltages of “B” Banks?
Distribution-level voltages
- 33kV
- 16kV
- 12kV
- 4kV
- 4.8kV
- 2.4kV
What are “C” Banks?
Special applications, they are connected to synchronous condensers, which are used to provide VAR support for voltage control.
As synchronous condensers are being from SCE’s system how are they being utilized?
For ground return for the subtransmission system. This ground return is necessary for proper protective relay operation.
What are Capacitor Banks used for?
To help improve system voltage.
How are capacitors made up?
A capacitor consists of two metal plates separated by an insulating dielectric. The metal strips are two aluminum foil strips, separated by a special paper dielectric (insulator) and rolled into packs. A number of these packs are assembled in a rectangular steel tank and connected in series and parallel groups to give the desired voltage and current rating. Bushings in the top of the tank bring out the leads from the capacitor packs.
What must be obtained before entering a capacitor bank enclosure?
A Clearance
What factors can switch on and off capacitors?
- Time of day
- Ambient temperature
- Load
- Volt/Time bias
As a first step apprentice, what is the main purpose for entering a substation?
Pick up materials or water for hot washing.
What must be done before entering an unmanned substation?
The Switching Center must be notified.
What do you do after you’ve entered an unmanned substation?
Lock the gates and keep them locked until you are ready to leave the property.
What is the process for entering a substation?
- ) Contact the Switching Center for approval to enter
- ) Do not use cell phones or two-way radios
- ) Extinguish any smoking materials
- ) Do not touch the gate with both of your hands at the same time
- ) Do not take conducting objects into work areas
- ) Park only in approved areas
What are the Safety Rules to be followed while in a substation?
- ) Make proper recording of your arrival in the substation logbooks
- ) Keep the gate closed and locked
- ) Leave your keys
- ) Walk on the rock dust or driveways while inside
- ) Confirm your entry
- ) DO turn on the Control House lights
- ) Do NOT touch the Control Panels
- ) Stay off the cable tranches
- ) Keep your hands and arms close to you
- ) Respect the barricades and signs
- ) Keep your PPE on at all times.
What do you use the Red Logbook for?
When logging clearances
What do you use the black logbook for?
General logs
What are the safety rules to be followed while exiting a substation?
- ) Make proper recording of your departure in the substation logbook, write down the same information entered when you first came in the substation. Describe, all the events; expected and unexpected, that took place while in the substation
- ) Make sure the gate is locked when you exit. To protect everyone, never leave a substation gate unlocked.
