2 Arc Flash Solutions for Low Voltage and New Energy

Arc flash solutions are more and more important in switchgears as serious burnout accidents of medium-voltage switchgear caused by arc short-circuit accidents occur from time to time. For example, when an arc fault occurs in a medium-voltage switchgear, the instantaneous power can reach up to 40MW, and the internal temperature of the arc can reach 10,000-20,000°C. Under the action of a high-energy arc and fault current for a long time, the switchgear itself will be damaged, and the transformer will also be severely impacted or damaged. If the arc fault is not removed in time and develops into a medium-voltage bus fault, the harm is very serious. It is even caused the collapse of electricity consumption in power plants and power outages for large-scale users. The arc flash protection relays can avoid above problem and are one of common arc flash solutions to protect your equipment from arc flash or arc fault.

What are the cause of arc flash in switchgears?

1. Insulation fault
The main reason is that the insulation material in the switchgear has insufficient creepage distance, does not meet the requirements of reinforced insulation, and insulation failure occurs in dirty environments and wet weather. In addition, due to the defect of the insulating material, the insulation of the switchgear with a long service life will age under the action of a strong electromagnetic field, which may also cause insulation damage and cause failure.

2. Poor current-carrying circuit
Due to the insufficient cross-section of some joints, loose fastening bolts, and poor contact of the handcart cabinet contacts, heating will be caused when a large current flows, and fire will cause phase-to-phase, relative breakdown, and so on.

3. Entry of foreign objects
For example, small animals (mice, etc.) enter the switchgear, or maintenance personnel leaves tools in the switch cabinet after the work is completed.

4. The operation is wrong
Such as wrong intervals, misoperation, failure to ground the working area, failure to conduct electrical inspection on the working area, etc.

5. System Aspects
Such as the increase of system capacity, change of grounding method, an increase of cable application, improper configuration of protection and automatic control devices, system resonance overvoltage, etc.

What is the common arc flash solutions for switchgear arc flash?

Nowadays, the arc flash protection relay is used to cut off arc flash or arc faults on the bus. For example, in the transformer backup, the transformer backup will not cooperate with the feeder and bus section switch, the protection trip time is generally set at 1.0-1.4S, and some even as long as 2.0S or more. To quickly remove the medium-voltage bus arc faults, the arc flash protection relay is needed. In switchgear, the arc flash protection relay also play an improtant role. Take Blue Jay arc flash protection relay as an example, the arc flash rleay can confirm whether the switchgear is in normal operation. When the contact position of the busbar, cable, and circuit breaker is short-circuited and an arc fault or arc flash occurs, the short-circuit fault of the busbar can be quickly removed within 10ms. This can reduce a lot of unnecessary waste of manpower and material resources, and ensure the reliable operation of the power system.

Blue Jay arc flash protection relay function

- Reduce the damage of arc flash to the human body;
- Reduce the damage caused by arc short-circuit faults to equipment;
- Avoid damage to the dynamic stability of the transformer due to short-distance bus failure, and prolong the service life of the transformer;
- Shorten the removal time of arc flash faults and avoid causing heavy losses to the DC system in the station;
- Reduce the time of equipment downtime caused by arc flash faults, and restore power supply faster.

Blue Jay arc flash protection relay Application

Power substation
The busbar room and feeder cabinet of the electrical section of the thermal power plant
Wind farm step-up station collector line switchgear
Box-type substation
Large-scale DC rectifier cabinets in the aluminum and magnesium industry

To know more about Blue Jay arc flash relays, please contact us now at info@cqbluejay.com.

2 arc flash solutions with arc flash protection relay

Arc flash solution for Low voltage

As shown in the figure, the low-voltage part consists of a transformer and 10 low-voltage cabinets. It is recommended to use the bus arc flash solution for such projects.

1) Install the busbar arc flash protection relay in the 1-1 incoming cabinet.

2) Install 3-4 arc light sensors in the transformer room (to expand the monitoring range).

3) Install 1-2 arc light sensors in the busbar room of 1-1 to 1-10 low-voltage cabinets (considering the coverage of the photosensitive area).

4) All sensors are uniformly connected to the busbar arc flash protection relay.

5) The busbar arc protection relay is connected to the protection current of the incoming cabinet as the current criterion. It can also be connected to the high-voltage side current of the transformer as the current criterion.

6) When an arc flash occurs in the switchgear and the current of the incoming cabinet is greater than the set value, the arc flash protection relay sends a trip signal to trip the switch of the incoming cabinet.

7) When an arc flash occurs in the transformer cabinet and the current on the high-voltage side of the transformer is greater than the set value, the arc flash protection relay sends a trip signal to trip the upper switch of the transformer.

Arc flash solution for New Energy

As shown in the figure, the converter cabinet of the wind power generating set can be installed with an arc protection device to protect the entire generating set. The arc sensor transmits the arc signal to the arc monitor, and the arc monitor judges the intensity of the arc, combined with the overcurrent signal transmitted by the current sensor, the double criterion of arc and overcurrent, comprehensively judges, and sends a tripping signal to the circuit breaker so that the circuit breaker Disconnect the fault circuit to avoid fault escalation and expansion.

1) Install 3-4 arc light sensors in the converter cabinet (to expand the monitoring range) to monitor the entire busbar.

2) All sensors are uniformly connected to the main control unit of busbar arc protection.

3) The main control unit of busbar arc protection is connected to the protection current as the current criterion.

4) When an arc occurs in the switch cabinet and the protection current is greater than the set value, the arc protection sends a trip signal to trip the circuit breaker switch.