Rîga Parzûna Têkiliyê: Yekêbûnê Têkiliya Pêşkêşkirin
Feeder protection relay yek cihaz e ku hêsan dike da ku feederên sistemê ya elektrik ji çewtiyên din derbas bike, wê çewtiyan jî bixweber short circuits, overloads, ground faults, û broken conductors. Feeder yek line yên transmission û distribution e ku şer û dema nûketi yên load û substation ê digere. Feeder protection relays yekşêl ên dike da ku reliability û security ya sistemên elektrik bişopînin, çunkî wan dibe ku çewtiyan biguheztin û îzole bikin, daneyışina malperan peyda bikin, û outage'ên elektrik minimiz bikin.
Distance Protection Relay Çi ye?
Yek ji tîpanên herêmî yên feeder protection relays yek distance protection relay e, yek impedance relay de. Distance protection relay impedance (Z) yek feeder line pîvandin dike nav berî voltage (V) û current (I) inputs ji potential transformer (PT) û current transformer (CT). Impedance bi vî rêya hatiye hesab kirin: Z = V/I.
Distance protection relay measured impedance bi value setting predefined pirsgirtin, ku maxîmum allowable impedance ji bo normal operation wekî nirxek hatiye tayîn kirin. Eger measured impedance li vir reng value setting be, ew dide ku hêdî û fault di feeder line de ye, û relay trip signal ji bo circuit breaker bişînin da ku fault îzole bikin. Relay dikarin jî parameterên fault, wê fault current, voltage, resistance, reactance, û fault distance, li ser screen display bikin.
Fault distance distance ji location ya relay ji bo location ya fault e, ku bi multiply measured impedance ji line impedance per kilometer hatine estimate bikin. Mînak, eger measured impedance 10 ohms û line impedance per kilometer 0.4 ohms/km be, fault distance 10 x 0.4 = 4 km. Dan fault distance dikare ku fault bi tevistîn hatine locate û repair bikin.
Quadrilateral Characteristic Çi kerê?
Distance protection relay dikarin ji operating characteristics din, wê circular, mho, quadrilateral, û polygonal. Quadrilateral characteristic yek choice popular e ji bo modern numerical relays çunkî piştgiriya flexibility û accuracy ji bo setting protection zones.
Quadrilateral characteristic yek graph shaped parallelogram e ku protection zone ya relay define dike. Graph four axes hatiye: forward resistance (R F), backward resistance (R B), forward reactance (X F), û backward reactance (X B). Graph jî slope angle hatiye, relay characteristic angle (RCA), ku shape ya parallelogram determine dike.
Quadrilateral characteristic bi vî rêya steps plot bikin:
R F value li positive X-axis set bikin û R B value li negative X-axis set bikin.
X F value li positive Y-axis set bikin û X B value li negative Y-axis set bikin.
Line draw bikin ji R F bîr X F bi slope RCA.
Line draw bikin ji R B bîr X B bi slope RCA.
Parallelogram complete bikin bi connect R F bîr R B û X F bîr X B.
Protection zone li ser roja parallelogram e, ku mean dike ku eger measured impedance li ser area ya ku hatine werin, relay trip bikin. Quadrilateral characteristic dikare ku cover four quadrants of operation:
First quadrant (R û X values positive): Quadrant ya ku inductive load û forward fault ji relay re represent dike.
Second quadrant (R negative û X positive): Quadrant ya ku capacitive load û reverse fault ji relay re represent dike.
Third quadrant (R û X values negative): Quadrant ya ku inductive load û reverse fault ji relay re represent dike.
Fourth quadrant (R positive û X negative): Quadrant ya ku capacitive load û forward fault ji relay re represent dike.
Zones of Operation Çi ne?
Distance protection relay dikarin ji different zones of operation din, ku defined by different setting values of impedance û time delay. Zones designed to coordinate with other relays in the system û provide backup protection for adjacent feeders.
Typical zones of operation ji bo distance protection relay:
Zone 1: Zone ya ku 80% to 90% of the feeder length cover dikin û no time delay. Primary protection ji bo faults within this zone û trips instantaneously.
Zone 2: Zone ya ku 100% to 120% of the feeder length cover dikin û short time delay (usually 0.3 to 0.5 seconds). Backup protection ji bo faults beyond zone 1 û adjacent feeders.
Zone 3: Zone ya ku 120% to 150% of the feeder length cover dikin û longer time delay (usually 1 to 2 seconds). Backup protection ji bo faults beyond zone 2 û remote feeders.
Some relays may also have additional zones, such as Zone 4 for load encroachment or Zone 5 for overreaching faults.
Other Types of Feeder Protection Relays Çi ne?
Beside distance protection relays, there are other types of feeder protection relays that can be used for different applications û in combination with distance protection relays. Some examples are:
Overcurrent protection relays: These relays measure only current û trip when it exceeds a preset value. They simple, inexpensive, û widely used for radial feeders.
Differential protection relays: These relays compare current inputs from both ends of a feeder û trip when there is an unbalance between them. They fast, selective, û sensitive for short feeders or busbars.
Directional protection relays: These relays measure both current û voltage û determine their phase angle difference. They trip only when current flows in a specific direction relative to a voltage. They useful for looped feeders or parallel feeders.
Arc-flash detection relays: These relays use light sensors û high-speed overcurrent detection to identify arc-flash events on feeders. They trip faster than conventional relays û improve safety for personnel.
How to Select Feeder Protection Relays?
Selection of feeder protection relays depends on various factors, such as:
The type, length, configuration, loading, grounding, û insulation level of feeders
The availability, accuracy, cost, maintenance, communication, û integration of relays
The coordination, selectivity, sensitivity, speed, reliability, security, û stability of protection schemes
The standards, regulations, codes, policies, û practices of power system operators
Some general guidelines for selecting feeder protection relays are:
Choose numerical relays over electromechanical or static relays for better performance, functionality, flexibility, û diagnostics
Choose distance protection relays over overcurrent or differential protection relays for long or complex feeders
Choose quadrilateral characteristics over circular or mho characteristics for more accuracy û adaptability
Choose low-energy analog sensor inputs over conventional current/voltage inputs for reduced size, weight, û safety hazards.
Choose arc-flash detection relays over conventional relays for faster tripping û personnel safety.
Conclusion
Feeder protection relays vital devices ne ku hêsan dike da ku feederên sistemê ya elektrik ji çewtiyên din derbas bike. Wan dikarin reliability, security, û efficiency ya sistemên elektrik bi tevistîn biguheztin û isolate bikin, preventing damage to equipment, û minimizing power outages.
One of the most common types of feeder protection relays is the distance protection relay, which measures the impedance of the feeder line by using the voltage û current inputs from the corresponding potential transformer û current transformer. It compares the measured impedance with a predefined setting value, which represents the maximum allowable impedance for normal operation. If the measured impedance is lower than the setting value, it means that there is a fault on the feeder line, û the relay will send a trip signal to the circuit breaker to isolate the fault.
The distance protection relay can have different operating characteristics, such as circular, mho, quadrilateral, or polygonal. A quadrilateral characteristic is a popular choice for modern numerical relays because it offers more flexibility û accuracy in setting the protection zones.
A quadrilateral characteristic is a parallelogram-shaped graph that defines the protection zone of the relay. The graph has four axes: forward resistance (R F), backward resistance (R B), forward reactance (X F), û backward reactance (X B). The graph also has a slope angle called the relay characteristic angle (RCA), which determines the shape of the parallelogram.
The quadrilateral characteristic can cover four quadrants of operation: first quadrant (inductive load û forward fault), second quadrant (capacitive load û reverse fault), third quadrant (inductive load û reverse fault), û fourth quadrant (capacitive load û forward fault).
