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Basic knowledge of substation
2011-03-14 by seoer1

1, the role of Substation: substation is connected to power plants, power grids and power users of the intermediate links, the main collection and distribution of power, control operations, lifting the voltage and other functions.

2, the substation components:  3 Phase Power Transformer , high voltage electrical installations, low voltage distribution equipment and associated buildings.

3 substations Category
⑴ classification by role
① boost substation: power plants and power plants built in the vicinity of the generator voltage is increased and then connect with the power system, through the high-voltage electricity transmission lines will be sent to the user.
② step-down substation: built in electric load center, the pressure reduced to the required voltage levels for users.
③ hub substation: power systems together and contact number of large power lines and the establishment of the substation, the high-pressure side of the main power system in exchange for high-power-based, low-pressure side of the supply of electricity and other industrial and mining enterprises and residential lives.

⑵ classified by form of management
① substation was on duty: the resident attendant there, to monitor the operation of equipment, maintenance, operation, management, larger capacity of these substations.
② unattended substation: no permanent attendant, but by the control center elsewhere through the remote device or assign someone to check on the substation equipment, maintenance, operation at any time in case of equipment or stop sending people to switch to run , transmission.

⑶ classified by structural type
① substation outside the house: a device arranged outside the house. High Voltage Substation with this approach.
② house substations: electrical equipment are arranged in the house, the city densely populated areas or areas of serious contamination, the voltage at 110KV below with this approach.

Classified according to geographical conditions ⑷
Ground substation, underground substation.

4, the size of substation
By voltage level, voltage transformers and levels of total capacity, said the number of outgoing circuits.
Voltage to rated voltage of the transformer, said high side, such as 35,110,220,330,500 KV substation.
The total capacity of the transformer is usually the main transformer at full capacity to represent the sum.
The number of outgoing circuits at all levels of voltage, according to the capacity of substations and industrial areas the user to determine. If a substation 35KV transmission line has five, four 110KV transmission line, three 10KV distribution line users, the outlet 12 of the total return.

5, an electrical substation equipment components: transformers, circuit breakers, isolating switches, current transformers, voltage transformers, overhead bus, arc suppression coil, shunt reactors, power capacitors, adjusting the camera and other equipment.

6, transformers
⑴ role: change the voltage, the voltage will be transformed into a level with the frequency of the voltage of another level.

Classification ⑵ transformer
① divided by number of phases: single-phase transformers, three phase transformers.
② According to Purpose: step-up transformer, step-down transformer and connect the transformer.
③ divided by winding: two-winding transformer (high voltage and low voltage of each phase winding each), three-winding transformer (each phase are high, medium and low winding) and the auto-transformer (high and low pressure side of the share of each phase of a winding, from the high voltage winding center tap)

⑶ transformer structure
① Core: The silicon steel sheet coated with layers made of insulating paint used to form the magnetic flux coupling, called the core part of the winding sets of columns, core columns is generally trapezoidal cross section, the larger the diameter of the core stack film of oil between the left channel, to facilitate cooling, the connection part of the core columns, said yoke.
② winding: a conductive part of the transformer, insulating materials copper or aluminum wire wound into a cylindrical shape, and then cylindrical high and low voltage winding in the core set of concentric column, low-voltage winding near the core, high voltage winding outside, so place is conducive to the insulation between the winding core.
③ tap: the use of changing the winding approach to regulating the number of turns. Will lead to the number of windings called tap tap, tap of the device for switching said tap; sub-divided into no-load tap-tap-tap-and-load, no-load transformer tap-only case of power failure, can switching; a load tap can be switched with the load condition.
④ Protection:
a, storage cabinets (oil pillow): regulating oil and reduce oil and air between the contact surface, thereby reducing the  Electrical Power Transformer oil damp and decay.
b, absorption devices (respirators) to maintain the tank pressure is normal, dehumidifiers built with silica gel, to absorb the oil into the water in the air pillow.
c, secure airway (explosion-proof tube): It's the exit with glass or thin iron plate, when the transformer internal failure, external exhaust gas flow to break the glass in order to reduce pressure inside the tank to prevent explosion.
d, gas relay: When the transformer internal fault, the transformer tank of gas to produce a large number of actions to cut off the transformer power supply, protection of transformers.
e, oil purifier (thermal siphon filter): the use of the natural cycle of the oil so the oil through the adsorbent filter, purify and prevent the aging of the oil.
f, Thermometers: Monitoring the transformer tank to measure the top oil temperature, mastered the operational status of the transformer.

⑷ transformer cooling
① oil from the cooling: the transformer core and winding directly immersed in the oil tank, the transformer in the operation of the heat generated by the transformer oil delivered to the tank wall and radiator pipes, the use of radiation and the wall and around the box air convection, the heat away, reducing the transformer temperature rise.
② air-cooled oil: In order to speed up the cooling transformer oil in the radiator is equipped with a fan to speed air flow, rapidly cooling the oil, to reduce the temperature of the purpose of the transformer.
③ forced air-cooled or water-cooled oil circulation: with special pumps, forcing the oil circulating in the radiator, with the radiator cooling fan speed or the use of special equipment, the water in transformer oil through the radiator to remove heat, to cool the transformer purposes.

7, circuit breakers
⑴ breaker role: put the device through the circuit breaker (ON) or out (disconnected) operation. When electrical equipment or line failure, the motor control relay circuit breakers, so that faulty equipment or lines quickly removed from the power system to ensure trouble-free equipment in power system operation.
⑵ breaker composition: breaking components in support of insulation components, transmission components, base and actuator components.
⑶ Circuit Breaker
① classified according to voltage levels: level divided by the voltage circuit breaker (10,35,110,220,330,500 KV) and low-voltage circuit breaker (400V).
② Classification by arc media: less oil or circuit breaker (oil is only used interrupter, the insulation of live parts with a ceramic or organic insulating materials, oil less), multi-oil circuit breaker (oil not only for insulation, but also to interrupter, oil and more), air circuit breakers (using compressed air only for insulation, but also to interrupter), vacuum circuit breakers, circuit breaker sulfur hexafluoride (SF6 gas-arc and the insulation), and auto gas and magnetic circuit breakers blow.
③ Classification by installation environment: outside the house type and house type.

⑷ circuit breaker to run the main technical parameters and the basic requirements
⑴ main technical parameters: Rated current, rated voltage, rated breaking current opening time, closing time, and dynamic stability and thermal stability of current.
⑵ run basic requirements: operational reliability, breaking capacity sufficient to meet the requirements of power system opening time, to achieve the reclosing, simple structure, low prices.

8, isolation switch
⑴ isolation switch roles: the live parts of electrical equipment and isolated to ensure the electrical equipment to safely carry out maintenance or troubleshooting; change the operation mode (as in the double-bus wiring circuit, device or may be from a group of bus lines switch to another group on the bus)

Classification ⑵ isolation switch
① classified according to the installation site: the house type and house type
② Classification by the number of insulating pillars: Single column type, double column type, the three orders.
③ Classification by use: use of transmission and distribution, with Generator Lead, neutral grounding transformer sub-use and fast in four.
④ closed by grounding both sides of blade fracture is classified: One earth, two grounded and ungrounded three.
⑤ movement by way of contact Classification: horizontal rotation, vertical rotating, swinging, and plug-in.
⑥ active actuator by Category: manual, electric and pneumatic manipulation.
⑦ by poles into pole and three pole isolating switch.

⑶ the basic requirements of the isolation switch
① there are obvious disconnect point, easy to identify whether the power supply disconnected.
② break points, the insulation should be reliable, that there is enough distance, in poor weather conditions or over-voltage alternating flashover situation, not click through from the disconnect to ensure the safety of maintenance personnel .
③ operation should have sufficient thermal stability and dynamic stability, especially not because of the role of electric power automatically disconnected, otherwise it will cause a major accident.
④ structures are as simple as possible, and reliability, on the ground with a knife in the isolation switch, must have locking devices to ensure that disconnect and then close the isolating switch or disconnect the earth ground knife blade and then close the isolation switch operating requirements.

9, CT
Transformer is high voltage and high current Power station Transformers  into a meter or protection devices for low voltage and current.

⑴ role:
① with the transformer and measuring instruments, equipment and line voltage, current, power, etc. were measured.
② transformer and relay or protection device with, for electrical equipment, power system protection equipment.
③ make the measuring instrument transformers, protection devices and high voltage electrical equipment isolation, to ensure the safety of operation attendant and secondary equipment safety.
④ the circuit voltage and current transformation into a unified standard value for the benefit of meters, relays and other secondary equipment standardization.

⑵ Transformer Classification
① type voltage transformer
a, inter-sensor electromagnetic voltage: Single phase dry type, three-core five-column, single-phase oil-immersed and immersed cascade and so on.
b, capacitor voltage transformers: single-phase oil-immersed, which consists of capacitive divider and electromagnetic unit structure.
② the type of current transformer
① Dry type current transformer: through type, bus type, support type three, with the days of generator circuit and the switch cabinet.
② oil-immersed current transformers, power distribution devices used for outdoor.
③ cascade current transformer, several intermediate current transformer in series with each other.
④ time box each sensor Capacitive Current

10, arc suppression coil: The main point is not used directly grounded neutral power system, when the metallic phase occurs when the ground fault, compensation ground capacitive current, so the value of the allowed range.
Arc suppression coil is a coil with an iron core inductor, the core has a gap, in order to get a larger inductor current, the coil ground side of a number of taps in order to adjust the grade within a certain range the size of the inductor. Petersen Coil generally connected to the neutral point of transformer or generator.

11, the role of shunt reactor; weakened line in the no-load or light load capacitance effect, reduce the frequency over voltage; while taking advantage of one of the ground by low reactance to compensate for arc current, accelerated quenching Arc.

12, power capacitor
⑴ parallel compensation capacitors are used to increase the reactive power and raise the level of electrical voltage.
⑵ series capacitors for 220KV and above power system can improve the transmission line capacity, system stability and a reasonable distribution of capacitance between parallel lines. 110KV and below in the system, can improve the level of line voltage and improve the distribution network transmission capacity.
⑶ STATCOM controlled by the capacitor and saturable reactor components, both stressed the advantages of the camera and capacitors.

13, adjusting the camera: in fact it is a no-load operation of the synchronous motor, mounted in the load center of the substation, to supplement the reactive power, improve power factor.

14, bus
⑴ power plants and substations in the voltage distribution equipment in the bus at all levels, all kinds of electrical connection between the wires and generators, transformers and other electrical equipment and the corresponding connecting wire between the power distribution unit, said bus.

⑵ function: convergence, distribution and transmission power.

⑶ bus usually aluminum; continuous current is large, and the location and the narrow outlet end of the transformer and the environment on the corrosion of aluminum, the selection of copper; 110KV and above power distribution device, when using a hard wire, it must have sufficient mechanical strength and safety factor, commonly used aluminum manganese alloy.
⑷ conductor (body) of the cross section
① rectangular bus: in the house more than 35KV power distribution equipment, most of the bus with rectangular cross section, rectangular bus bar heat better.
② circular coil: 35KV power distribution equipment above the house, most with circular cross-section bus. Because non-circular cross-section the electric field concentration in the wire will not cause corona. 110KV and higher voltage in the outdoor distribution equipment, the general use of aluminum wire or steel core aluminum tubular bus.
③ high current bus: For the large-capacity generators, due to the work of current large, rectangular bus bar can be used to increase the number of load flow. Each cross-section the same thickness with the same distance bus to facilitate heat dissipation. When the three rectangular bus bar per phase can not meet the requirements, can be slotted bus.
④ water-cooled bus: Bus carrying capacity several times higher than normal for the water cooled generator windings.

15, insulator
⑴ insulator role: to support the wires, and make insulation devices.
Classification ⑵ insulator
① BY PURPOSE: high voltage insulators: electrical insulators and power line insulator.
Low-voltage insulators for low voltage overhead lines, low voltage wiring, telecommunications lines.
② Press the main points of insulating material: porcelain insulators, glass insulators, organic materials, insulators and composite insulators.
③ by the structure: A type, B type and high-pressure casing. High-pressure casing for the wires through the walls, shell boxes, etc., and to the conductor and the wall, boxes, shells and other insulation. High-pressure liquid-filled casing casing points, inflatable tube, oil impregnated paper capacitor bushings and casing.

16, the concept of substation secondary circuit
⑴ components: an electrical substation secondary circuit routing measuring instruments, monitoring devices, signaling devices, control and synchronization devices, relay protection and automatic device and other components.
⑵ role: to ensure an electrical equipment safety, reliability and an important part.
⑶ tasks: monitoring an electrical power system equipment and working conditions, an electrical control equipment, and in electrical equipment and power a system failure can make some quick out of operation or failure to provide signals attendant to take measures in time .

17, measurement and monitoring: To ensure safe operation of electrical equipment must be installed measuring instruments and record-type instruments, synchronization settings, insulation monitoring devices, these instruments and devices and voltage transformers, current transformers connected to the secondary winding.

18, signal circuit
⑴, accident signal: When an equipment or power systems electrical accident occurs, such as the failure of any one cause for Tripping circuit breaker immediately after the audible signal and flashing signals to alert operating personnel to take measures to deal with. Accident signal to repeat the action with nature.
⑵, notice signal: substation equipment does not occur when the normal operation and abnormal operation, audio signals must be given notice, while optical digital signal sent to notify attendant electrical equipment to run the health exception occurred, or suggest possible to run the personnel in the equipment cause accidents.

19, the operating power supply: substations, circuit breakers and other electrical equipment on the remote control, operation, signal, relay protection, automatic devices, run, have a dedicated power supply, the DC power supply.

⑴ battery DC system: battery, charger and float a separate motor and other components of DC systems. It is responsible for all electrical equipment substation operation of the power, signal power, relay protection and automatic equipment until the power supply. AC power lost when the substation, it is also important equipment supply emergency lighting and power.

⑵ DC rectifier capacitor energy storage system: silicon rectifier devices, communication systems obtained from the DC power supply, requires a reliable AC power. When a failure occurs, AC voltage drop, so that the DC system voltage drop, protection devices caused severe refused action. In order to protect the devices and ensure reliable operation of the circuit breaker failure tripping device, the use of capacitor energy storage device by an electrical discharge, so that protection and reliable operation.

⑶ double rectification DC system: double rectifier and rectifier with capacitor energy storage device as a DC power supply, save construction investment cost, the disadvantage is that when AC power all but disappeared, do not lose the risk of operating power.

20, relay protection and automatic safety device
⑴ protection and security automatic device's basic requirements: reliability, safety, sensitivity, selectivity, speed and mobility.

⑵ protection Category: main protection and backup protection. Primary protection in the event of failure to correctly and reliably the first action, in the shortest time or without time to removal of the fault within the scope of protection. If the transformer differential protection, high-frequency transmission line protection, distance protection, zero sequence current protection.
Backup protection when the protected electrical equipment, the main transmission line circuit breaker failure protection or the protection of works, such as transformers, transmission lines over-current protection.

⑶ automatic safety devices: automatic reclosing transmission lines such as equipment, auxiliary power BZT devices, substation bus or bus segment BZT, automatic load shedding by frequency devices, electrical braking and automatic cutting machine devices.

21, the main substation wiring
(1) single-bus connection: power supply and delivery outlet is connected to a public bus.
Advantages: Wiring is simple, easy operation, low investment;
Disadvantages: As the power outlet and connected to a bus send, when the power circuit breaker or bus failure, power failure will cause the whole reach of the user, so wiring is only applicable to small power plants or substations.
⑵ Double Busbar (single breaker double bus): There are two buses, one group to another group working backup, you can work simultaneously. Two bus connections by bus coupler circuit breaker. Each is equipped with a circuit breaker, disconnecting switch, and two were connected to two bus.
Advantages: The maintenance bus or bus coupler circuit breakers, do not interrupt power to the user; when a bus fails, the other group on the bus can continue to supply, reduce the power range; when any one circuit breaker failure, can switching operation mode, instead of by the mother of the fault circuit breaker; operation flexible.
Disadvantages: complex wiring in the switching operation, the possibility of misuse occur; As a result of too much equipment, construction investment is large. For medium-sized thermal power plants, substations and EHV substation.
(3) with a bypass bus, single breaker double bus connection: When a circuit breaker maintenance, failure, can be bypassed by the bypass bus bus circuit breaker electricity supply to consumers. Improve the flexibility and power to run the security, reliability, continuity.

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