SUBSTATION EQUIPMENTS

The major components of a typical substation are:

Air Circuit Breaker Distribution Bus PotheadsBatteries Duct Runs Power-line CarrierBus Support Insulators Frequency Changers Power TransformersCapacitor Bank Grounding Resistors RectifiersCircuit Switchers Grounding Transformers Relays

Concrete Foundation High-Voltage Underground Cables

SF6 Circuit Breakers

Conduits High-Voltage Fuses Shunt ReactorsControl House Lightning Arresters Steel SuperstructuresControl Panels Manholes Supervisory ControlControl Wires Metal-clad Switchgear Suspension InsulatorsConverter Stations Meters Synchronous CondensersCoupling Capacitors Microwave Transmission BusCurrent Transformers Oil Circuit Breakers Vacuum Circuit BreakersDisconnect Switches Potential Transformers

Air circuit breakers are used to interrupt circuits while current flows through them. Compressed air is used to quench the arc when the connection is broken.

Bus support insulators are porcelain or fiberglass insulators that serve to isolate the bus bar switches and other support structures and to prevent leakage current from flowing through the structure or to ground. These insulators are similar in function to other insulators used in substations and transmission poles and towers.

Capacitors are used to control the level of the voltage supplied to the customer by reducing or eliminating the voltage drop in the system caused by inductive reactive loads.

Circuit switchers provide equipment protection for transformers, lines, cables, and capacitor banks.

They also are used to energize and deenergize capacitor banks and other circuits. 

Conduits are hollow tubes running from manhole to manhole in an underground transmission or distribution system. They can contain one or more ducts (See Duct Runs). They can be made of plastic (PVC), fiberglass, fiber, tile, concrete, or steel. PVC and fiberglass are most commonly used.

The substation control house contains switchboard panels, batteries, battery chargers, supervisory control, power-line carrier, meters, and relays. The control house provides all weather protection and security for the control equipment. It is also called a doghouse.

Converter stations are located at the terminals of a DC transmission line. Converter stations can change alternating current into direct current or change direct current to alternating current. Sometimes converter stations are located at a generation power plant or at transmission substations. Two unsynchronized AC transmission systems can be connected together with converter stations.

Converter stations are also found in most substations for converting the emergency battery back-up system to AC power for use in an emergency.

Coupling capacitors are used to transmit communication signals to transmission lines. Some are used to measure the voltage in transmission lines. In signal transmission the coupling capacitor is part of a power line carrier circuit as shown in the schematic below. A coupling capacitor is used in this circuit in conjunction with a line trap. Line traps can be installed at the substation or on a

transmission line tower. 

Primary coupling capacitor

Current transformers can be used to supply information for measuring power flows and the electrical inputs for the operation of protective relays associated with the transmission and distribution circuits or for power transformers. These current transformers have the primary winding connected in series with the conductor carrying the current to be measured or controlled. The secondary winding is thus insulated from the high voltage and can then be connected to low-voltage metering circuits.

Current transformers are also used for street lighting circuits. Street lighting requires a constant current to prevent flickering lights and a current transformer is used to provide that constant current. In this case the current transformer utilizes a moving secondary coil to vary the output so that a constant current is obtained.

400 kV current transformer

Pole type constant current transformer

Disconnect switches or circuit breakers are used to isolate equipment or to redirect current in a

substation. Many different types of disconnect switches are shown below.

Disconnect switches on an outgoing distribution circuit

A distribution bus is a steel structure array of switches used to route power out of a

substation. The power goes from the transformer to the distribution bus.

Duct runs are hollow tubes running from manhole to manhole inside a conduit (see conduits) in an underground system. They are of various sizes usually from 2 to 6 inches in diameter. Electrical cables are run through ducts and the ducts are sized accordingly. The diameter of a duct should be at least 1/2 to 3/4 inch greater than the diameter of the cable(s) installed in the duct. They can be made of plastic (PVC), fiberglass, fiber, tile, concrete, or steel. PVC and fiberglass are

most commonly used.  

A frequency changer is a motor-generator set that changes power of an alternating current system from one frequency to one or more different frequencies, with or without a change in the number of phases, or in voltage. Sometimes a converter is used to accomplish this. 

Grounding Resistors are designed to provide added safety to industrial distribution systems by limiting ground fault current to reasonable levels. They are usually connected between earth ground and the neutral of power transformers, power generators or artificial neutral transformers. Their main purpose is to limit the maximum fault current to a value which will not damage generating, distribution or other associated equipment in the power system, yet allow

sufficient flow of fault current to operate protective relays to clear the fault. 

A grounding transformer is intended primarily to provide a neutral point for grounding purposes. It may be provided with a delta winding in which resistors or reactors are connected.

High-Voltage underground cables are constructed in many different ways, but are usually shielded cables. They are made with a conductor, conductor-strand shielding, insulation, semi-conducting insulation shielding, metallic insulation shielding, and a sheath. The sheath can be metallic and may then serve as the metallic insulation shielding and be covered with a nonmetallic jacket to protect the sheath. This sheath helps to reduce or eliminate inductive reactance. Such cables are commonly used in circuits operating at 2400 volts or higher.

High voltage fuses are used to protect the electrical system in a substation from power transformer

faults. They are switched for maintenance and safety. 

Lightning arresters  are protective devices for limiting surge voltages due to lightning strikes or equipment faults or other events, to prevent damage to equipment and disruption of service. Also called surge arresters.

Lightning arresters are installed on many different pieces of equipment such as power poles and towers, power transformers, circuit breakers, bus structures, and steel superstructures in substations.

A manhole is the opening in the underground duct system which houses cables splices and which cablemen enter to pull in cable and to make splices and tests. Also called a splicing chamber or cable vault.

Switchgear can be either for outdoor use or indoor use. An outdoor metal-clad switchgear is a weatherproof housing for circuit breakers, protective relays, meters, current transformers, potential transformers, bus conductors, and other equipment. An indoor switchgear must be protected from the environment and contains the same types of equipment as the outdoor type.

Various types of meters are found in substation control houses. They all are measuring devices and can be an indicating meter or a recording meter. An indicating meter shows on a dial the quantity being measured. A recording meter makes a permanent record of the quantity being measured, usually by tracing a line on a chart or graph. 

Substations commonly use microwave communication equipment for communication with local and regional electric power system control centers. This system allows for rapid communication and signaling for controlling the routing of power.

Electric power for microwave transmission comes from special transformers that reduce incoming transmission voltage to that required for the microwave system.

Oil circuit breakers are used to switch circuits and equipment in and out of a system in a substation.

They are oil filled to provide cooling and to prevent arcing when the switch is activated. 

A type of insulator with a bell or pot-like shape used to connect underground electrical cables to overhead lines. It serves to separate the bunched-up conductors from one another in the cable to the much wider separation in the overhead line. It also seals the cable end from the

weather. Potheads are mounted on a distribution pole and the assembly is called a riser pole.

Capacitor Voltage Transformers (CVT), are used for voltage metering and protection in high voltage network systems. They transform the high voltage into low voltage adequate to be processed in measuring and protection instruments secondary equipment, such as relays and recorders).  A Voltage Transformer (VT) isolates the measuring instruments from the high voltage of the monitored circuit. VTs are commonly used for metering and protection in the electrical power industry.

 

Main applications of CVTs in HV Networks Voltage Measuring: They accurately transform transmission voltages down to useable

levels for revenue metering, protection and control purposes Insulation: They guarantee the insulation between HV network and LV circuits ensuring

safety condition to control room operators HF Transmissions: They can be used for Power Line Carrier (PLC) coupling Transient Recovery Voltage: When installed in close proximity to HV/EHV Circuit

Breakers, CVT’s own High Capacitance enhance C/B short line fault / TRV performance 

Mechanical Features   Available with standard/heavy/very heavy creepage distance All external components are made by aluminum Inox steel bellows High earthquake strength capability Suitable for ambient temperature -60 / +70 °C (extended range upon request) Available for Line Traps mounting on the top

 

Electrical Features Best capacitance/accuracy stabilities in all service conditions Design solutions allow to reach High Rated Capacitance in reduced CVTs dimensions Passive ferroresonance suppression circuit provides superior damping while not

degrading transient response Best accuracy as transient performance – suitable for ultra-rapid line protection devices 

 

Type TCVT (for International Market)Types TECF, TECP, TEVF, TEMF, TEVP, TERP, TEMP, TETP, TEICF, TEIRF, TEIMF, TEHCF,TEHCP, TEHMF & TEHMP (for North American Market only)Available from 46 kV up to 1200 kVDesigned in accordance with main international standardsOptimized insulation system design utilizing state-of-the-art processing techniques witheither mineral oil or synthetic insulating fluidsComposite or Porcelain insulatorOil expansion by way of hermetically sealed stainless steel bellows assures the integrityof the insulation system over timeBellows puncture pin provides for release of internal pressure in the event of severe service conditions leading to internal discharges

High range of Customization according specific customer requirements