Rêlaya Parastina Bûyera

Pîşeyanê ya Parastina Feeder

Pîşeyanka parastina feeder dihewîne ji bo birarîna cihazek e ku parastin dikin berên sisteman de yên elektrikî ji ser çendkêşan û terheyan.

Pîşeyan împedansa (Z) berê ya feeder bi karîna potensiyel transformer (PT) û current transformer (CT). Împedans hesab dide bi bîra voltage (V) û current (I): Z = V/I.

Pîşeyan împedansa xwesta hatine da ku nîşan dide nîveka herî zorîn ji bo operasyon normal. Heke împedansa xwesta yekî ye, dema ku terheya be, pîşeyan signal trip dideyê breaker-a da circuit bi serparast kirina wê. Pîşeyan taybetmendiyên terheya wekî current, voltage, resistance, reactance, û distance-ya terheya di screen-a xwe de deket.

Distance-ya terheya diha ku derê pîşeyandan terheya ên hewceye, bi bîra împedansa xwesta û line impedance per km. Mînak, heke împedansa xwesta 10 ohms û line impedance per km 0.4 ohms/km be, distance-ya terheya 10 x 0.4 = 4 km. Dan dana ku hewce bikin û terheyan serparast bike.

Relay-ya Parastina Distance

Împedansa xwesta bi serparast kirina section-ê faulty.

Quadrilateral Characteristic

Relay-yan parastina distance dian jî taybetmendiyên operasyon ne, an jî circular, mho, quadrilateral, û polygonal. Quadrilateral characteristic populer e ji bo relay-yan numerical modern ji bo flexibility û accuracy-ya setting protection zones.

Quadrilateral characteristic grafik ên parallelogram-shaped e ku zone-ya parastina pîşeyan define dide. Grafik çar axis hewceye: forward resistance (R F), backward resistance (R B), forward reactance (X F), û backward reactance (X B). Grafik jî angle slope-an hewceye ku relay characteristic angle (RCA) name dide, ku shape-ê parallelogram determine dide.

Quadrilateral characteristic bi karîna vebijarkan bi ser:

• Set R F value li positive X-axis û R B value li negative X-axis.

• Set X F value li positive Y-axis û X B value li negative Y-axis.

• Draw line ji R F to X F bi slope-ê RCA.

• Draw line ji R B to X B bi slope-ê RCA.

• Complete parallelogram bi connecting R F to R B û X F to X B.

Zone-ya parastina di nav parallelogram de ye, ku manand û împedansa xwesta di area-ya ku hewceye, pîşeyan trip dide. Quadrilateral characteristic cover four quadrants of operation:

• First quadrant (R and X values are positive): This quadrant represents an inductive load and a forward fault from the relay.

• Second quadrant (R is negative and X is positive): This quadrant represents a capacitive load and a reverse fault from the relay.

• Third quadrant (R and X values are negative): This quadrant represents an inductive load and a reverse fault from the relay.

• Fourth quadrant (R is positive and X is negative): This quadrant represents a capacitive load and a forward fault from the relay.

Zones of Operation

Relay-yan parastina distance dian zones of operation ne, defined by impedance settings and time delays. These zones coordinate with other relays to provide backup protection for adjacent feeders.

The typical zones of operation for a distance protection relay are:

• Zone 1: This zone covers 80% to 90% of the feeder length and has no time delay. It provides primary protection for faults within this zone and trips instantaneously.

• Zone 2: This zone covers 100% to 120% of the feeder length and has a short time delay (usually 0.3 to 0.5 seconds). It provides backup protection for faults beyond zone 1 or in adjacent feeders.

• Zone 3: This zone covers 120% to 150% of the feeder length and has a longer time delay (usually 1 to 2 seconds). It provides backup protection for faults beyond zone 2 or in remote feeders.

• Some relays may also have additional zones, such as Zone 4 for load encroachment or Zone 5 for overreaching faults.

Selection Criteria

• Choose numerical relays over electromechanical or static relays for better performance, functionality, flexibility, and 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 and adaptability

• Choose low-energy analog sensor inputs over conventional current/voltage inputs for reduced size, weight, and safety hazards.

• Choose arc-flash detection relays over conventional relays for faster tripping and personnel safety.

Conclusion

Feeder protection relays are vital devices that protect power system feeders from various types of faults. They can improve power system reliability, security, and efficiency by quickly detecting and isolating faults, preventing damage to equipment, and 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 and current inputs from the corresponding potential transformer and 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, and 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 and 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), and backward reactance (X B). The graph also has a slope angle called the relay characteristic angle (RCA), which determines the shape of the parallelogram.