One, power system is basic concept
1, power system definition
Mix by the transformer inside network of the dynamo inside power plant, power all sorts of equipment using phone of transmission network and user, according to the unified whole that definite pattern joins and forms, call power system.
2, the composition of power system
Power system reachs electric energy user by network of the dynamo of power plant, power (the equipment that use phone) of composition.
3, grade of power system voltage
The system is rated voltage: Power system is various of voltage network nominal voltage value.
Rated voltage is worth the system is: 220V, 380V, 3kV, 6kV, 10kV, 35kV, 63kV, 110kV, 220kV, 330kV, 500kV, 750kV.
4, power facilities
The electric equipment cent of power system is equipment and 2 equipment, equipment (also say advocate equipment) it is the principal part that makes power system, it is the straightforward production, equipment that carry and distributes electric energy, include cable of generator of transformer of dynamo, electric power, breaker, switch-disconnector, power, power and transmission network to wait. 2 equipment is right equipment undertakes controlling, adjust, protection and monitored equipment, it includes to control appliance of implemental, protection and automatic device, measuring instrument watch, signal to wait. 2 times equipment passes voltage transformer and voltaic transformer and equipment to acquire electric connection.
2, power system breakdown and its harm
Every causes power system to run any abnormal join or circumstance to all call the breakdown of power system. The breakdown of power system has a variety of kinds, be like the short circuit, combination that breaks line or them. Short circuit weighs transverse breakdown again, break a line to call fore-and-aft breakdown again.
Short circuit breakdown can be divided for short circuit of three-phase short circuit, single-phase ground connection (abbreviation is single-phase short circuit) two-phase short circuit and short circuit of two-phase ground connection, noticing two-phase short circuit and short circuit of two-phase ground connection is the short circuit breakdown of two kinds of different property, former in flowing into the ground without short-circuit current, and latter has. Loop of the three-phase when three-phase short circuit is symmetrical as before, reason calls symmetrical short circuit; Other a few kinds of short circuit all make three-phase loop asymmetry, because this calls asymmetry short circuit.
The breakdown that break a string can be divided for single-phase break line and two-phase to break a string. Break a line to call blame complete photograph to move again, also be breakdown of a kind of asymmetry. Most circumstance falls to there is one to handle trouble only in power system, call simple breakdown or only heavy trouble, but may have two place sometimes or breakdown of two place above is coinstantaneous, call complex breakdown or multiple breakdown.
Once short circuit breakdown happens, often cause very serious consequence, basically have:
(1) electric current increases quickly. The electric current when short circuit should compare regular job electric current to be gotten greatly much, serious when ten times what can amount to normal electric current. Large dynamo gives a line to carry three-phase short-circuit current to be able to be amounted to tens of thousands of even ten. So big electric current will produce tremendous wallop, make electric equipment is out of shape or damage, meet a large number of giving out heat make at the same time equipment overheat and attaint. Sometimes the electric arc that short circuit dot produces may burn out directly equipment.
(2) voltage drops substantially. When three-phase short circuit, the tension that short circuit hints is 0, the voltage near short circuit dot also drops apparently, this will bring about the equipment that use phone to cannot work normally, for example asynchronous electromotor rotate speed drops, stop even turn.
(3) the stability that the likelihood makes power system moves is destroyed. After power system short-circuits, the electromagnetism power that the dynamo outputs decreases, and the mechanical power that prime mover inputs has not enough time to decrease accordingly, appear thereby lopsided power, this will bring about dynamo rotor to quicken. Some dynamoes are quickened fast, some dynamoes are quickened slow, make thereby dynamo mutual the differential seat angle between is bigger and bigger, this is caused possibly paratactic the dynamo that move loses synchronism, destroy systematic stability, cause big district power failure.
(4) lieutenant general of the system when asymmetry short circuit has shed lopsided electric current, the induction in the communication circuitry of parallel of meeting in the vicinity of gives very tall electromotive force and very big electric current, generate interference to communication, create risk possibly also to equipment and person.
In above consequence, the most serious is power system the destruction of paratactic moving stability, by the disaster that analogy is national economy, increase quickly be electric current next.
Besides, status of a few abnormal jobs still may appear in power system, if electric equipment exceeds rating to move (had called negative charge) , it also will make electric equipment insulation quickens ageing, cause breakdown hidden trouble to develop trouble even; Be like a dynamo especially the demote below the frequency of the cooling system breakdown of transformer of the oscillation of system of the overvoltage that the water turbogenerator swings bear suddenly to cause stator winding, power, electric power and dynamo and power system. The breakdown in the system causes power system accident possibly with abnormal moving condition, make regular job of the system is destroyed not only, cause electric equipment breakdown and person casualties possibly even.
3, power system protection
Power system has very close together report or electromagnetism connection between medium each component, once a certain component malfunctions, electric information will travel everywhere to the system with the speed of similar light. This kind of breakdown is impossible to move a method to eliminate and must with artificial hand the device of high speed automation eliminates. This is to make sure power system safety runs the most effective method.
The technical course of the automatic device that power system protection studies this kind to identify breakdown automatically to remove breakdown element side by side namely. That is to say, protection is automatic device is to be able to react in power system electric component breakdown or run state out of order and movement at breaker tripping operation or a kind of when issue demonstrative signal automatic device.
1, the action of protection
1) automatic, rapid, have alternative excise breakdown component from inside power system, make breakdown component is avoided destroy at continueing to suffer, make sure share of without reason block returns to normal quickly move.
2) reaction is electric the abnormal moving condition of component, uphold a requirement according to moving, and movement at giving out signal or tripping operation.
2, protection unit
When the power cell in power system (wait like dynamo, circuitry) or when power system itself produced breakdown to endanger power system safety to move, can to moving watch member issue admonitory signal in time, the measure of a kind of automation that perhaps issues tripping operation command to develop in order to end these event to place pilot breaker directly and equipment. Realize the whole set of equipment of measure of this kind of automation, connect commonly call protection unit.
3, the composition of protection unit and working principle
General protection unit by measure compare component, logistic judgement component and executive output component 3 parts composition.
1) measure compare component: Measure the physical parameter that carries the power cell that is protected, and with given the value undertakes comparative, according to relative result, give out " be " , " blame " , " 0 " or " 1 " a group of logistic signal of property, judge protector to whether should be started thereby.
2) logistic judgement component: The property of the logistic signal that compares component output according to measuring, early or late ordinal, duration, the logistic concern with make protector is pressed particular decides the type of breakdown and limits, whether should make certainly finally breaker tripping operation, issue signal or not movement, send corresponding statement executive output share.
3) executive output component: Judge the statement that transmits partly according to logic, the tripping operation pulse that gives out start aside breaker and relevant behavioral information, issue warning or not movement.
4, the classification of protection
1) , classify by the boy or girl friend that is protected: Transmission network protection, dynamo protection, transformer protection, bus protection, electromotor protection.
2) , by protection the principle classifies: Voltaic protection, voltage protection, distance protection, differential protection, direction protection, 0 foreword protection.
3) , be reacted by protection breakdown type classifies: Protection of protection of alternate with short circuit, ground connection short circuit, v/LIT all over the ground a short circuit protection, protection that break a string, protection that lose a condition, protection that break magnetism has reached excitation protection to wait.
4) , the implementation technology classification that presses protection unit: Electromechanical protection, rectification protection, transistor protection, integrated circuit protection, tiny model is protected.
5) , protection measured value and the relation classification that make calm cost: Excessive is protected (measured value ﹥ makes calm cost) , the protection that owe an amount (measured value ﹤ makes calm cost)
6) , the action classification that removes by protection: Advocate protection, back-up protection, auxiliary protection.
Advocate protection is to show contented system stability and equipment safety ask, can excise the protection of breakdown of the circuitry that be mixed by protective equipment selectively with the rapiddest rate.
Back-up protection is to point to advocate protect or protect with what will excise breakdown. Divide again for close back-up protection and far back-up protection. Close back-up protection: In this component place furnish is protected two sets, when advocate when protective refus is moved, by the another protection act of this component. Far back-up protection: When advocate when protective refus is moved, realize mothball protection by another protection of this power facilities or circuitry; When breaker refus is moved, by breaker malfunction protects the back-up protection that will come true.
5, the main demand of protection:
Alternative, fast move gender, sensitivity, dependability;
Dependability is to point to to the movement answers when protecting this movement, ought not to when the movement not movement.
It is to point to optionally excise breakdown by the protection of breakdown equipment or circuit itself above all, when the protection of breakdown equipment or circuit itself or breaker refus are moved, just allow to protect excision breakdown by the protection of photograph adjacent equipment, circuitry or breaker malfunction.
Sensitivity is to point to in equipment or circuitry be protected when malfunctioning inside limits, protector provides the abundant of some right movement ability to spend, be described commonly with strain gauge factor.
Fast using a sex is to show protector should excise short circuit breakdown as soon as possible, its purpose is to increase systematic stability, reduce the attaint rate of breakdown equipment and circuitry, contractible breakdown affects limits, raise automatic coincide brake and reserve power source or reserve the effect that equipment throws automatically.
4, transformer substation is integrated automation system
Use the implementation such as advanced computer technology, contemporary electron technology, communication technology and information processing technology to transformer substation 2 equipment (include protection, control, measure, wave of collection of signal, breakdown, automatic device and telecontrol equipment) the function undertakes reset, optimize a design, the moving circumstance of entire to transformer substation facility carries out surveillance, measure, control and a harmonious kind of omnibus automation system. Through transformer substation inside integrated automation system information is exchanged each other between each equipment, data is shared, the transformer substation that finish runs surveillance and control errand.
