Fast protection of medium and low voltage busbars – Wienal

1.It is necessary to install arc light maintenance

Arc maintenance in foreign countries has nearly 20 years of history, the first set of maintenance equipment in 1995 has been put into operation, China's previous imported units in the introduction of foreign complete sets of arc light maintenance (such as Guohua Tianjin Panshan Power Plant), the first set of domestic units in 2000 began to operate, for the maintenance of the safe operation of equipment has played an important role. The generation of arc light is multifaceted, and the consequences are also very severe. The man-made causes of arc light in switchgear are: mistakenly entering the live interval; Misoperation of the barrier switch; Forgetting to ground in the work area; Forget to measure the voltage in the work area.

The technical reasons for the generation of arc light in switchgear are: equipment failure and misoperation of live equipment; After the equipment is overhauled normally, the lost tool is in the switchgear; Wrong wiring and busbar connections; Insulation aging and mechanical wear, overvoltage, small animals (especially rats), dust, temperature, humidity, corrosion, and other environmental factors.

The technical reasons for the arc light generation in the operation of the switchgear are: many arc light problems generated in the operation of the switchgear are mostly due to the influence of environmental conditions, so that the insulation material is damp, and the insulation surface of the equipment produces condensation and attached pollution, so the insulation level of the equipment decreases to form an incident

Fast protection of medium and low voltage busbars – Wienal

Fast protection of medium and low voltage busbars – Wienal

2. The hazards of arc light

The arc generated by the faulty cable spacing of the switchgear causes the pressure and temperature in the switchgear to increase rapidly, and if not removed in time, it will form major hazards in the following aspects:

(1) The arc temperature is equivalent to twice the solar temperature, about 10,000 °C, because overheating will cause the copper and aluminum bars to melt and gasify;

(2) Cable melting, ignition of cable cladding;

(3) Overheating causes the pressure to rise, causing the switchgear to burst;

(4) The switchgear vibrates strongly, which loosens the fixed elements;

(5) High temperature cauterizes the skin, and strong light stabs the eyes;

(6) It produces a lot of harmful gases and damages the respiratory system;

(7) Plastosis damage to eardrums and lungs;

(8) Debris flies, causing personal injury or even death.

The degree of harm of arc defects depends on the arc current and the moment of excision, and the energy generated by the arc increases exponentially and rapidly with I2t. As long as the total excision time is less than 85ms, the equipment will not suffer from harm, and the total excision time is greater than 100ms, which will form different degrees of harm to the equipment.

3. Examples of arc light problems

In August 1982, the Dajiaoting substation of Beijing Power Supply Bureau, because of continuous rain, caused water to enter the cable trench of the distribution room, and the insulation of the switchgear was damp, forming an interphase arc fault of the switchgear, burning 1 switchgear, burning 8 units, burning 4 current transformers, more than 40 pillar insulators, and 7 groups of blocking switches, resulting in power outages for several days.

From February to October 1986, Hunan Jinzhushan Power Plant produced six times of arc light in the 6kV switchgear of the plant, burning and burning 9 switchgears, nearly 100 pillar insulators, dozens of other equipment, forming a unit load dumping, and the furnace was shut down.

In 1985, when the Tianjin substation was closed and transmitted, the switchgear had arc light problems, which caused the arrester to burst and the power distribution room to catch fire, and burned 8 switchgears.

In 1986, the switchgear of a substation in Tangshan was misoperated during operation, and the insulating partition was scorched and caught fire.

From June to July 1987, the substation in the eastern suburbs of Jiaozuo, Henan Province, there were two incidents caused by the discharge of the insulating plate of the switch contact, the incineration of the circuit breaker, and the flashover and explosion of the insulator of the switch cabinet bus post, forming a three-phase short circuit.

At 9:35 a.m. on February 13, 2001, the 4# cabinet of the high-voltage distribution room of Shanghai Huayangqiao Dajiang Meat Food Factory was bursting due to the breakdown of white material insulation, and there were obvious traces of discharge and burns on the adjacent B phase busbar.

On November 4, 2000, a maintenance worker was burned by an electric arc in the carbonization chemical section of the ammonia workshop of a fertilizer plant in Anhui Province.

4. Now used for the maintenance of medium and low voltage busbars and their limitations

There are three types of maintenance commonly used in medium and low voltage bus systems:

(1) Transformer backup overcurrent maintenance (typical maintenance action time is 1.2s - 1.4s)

(2) Select the feeder quick-break maintenance lock-up transformer backup overcurrent maintenance (typical maintenance time is 300ms-400ms)

(3) High impedance maintenance (typical maintenance time is 35ms-60ms)

(1) and (2) are too long for the requirement that the total resection time is less than 100ms; The maintenance scope of (3) maintenance is limited by the CT installation location and is expensive. Arc light maintenance provides a trip output of 15ms, so the total cut-off time is 80ms to 100ms, and there is no visible damage to the switchgear.

Fast protection of medium and low voltage busbars – Wienal

Sections viewed

Contact

working hours