2023年简析电流互感器开路的危害原因现象及处理方法和防范措施.doc

简析电流互感器开路旳危害、原因、现象及处理措施和防备措施（Analysis of current transformer open circuit hazards, causes, phenomena, treatment methods and preventive measures）
简析电流互感器开路旳危害、原因、现象及处理措施和防备措施
(Analysis of current transformer open circuit hazards, causes,
phenomena, treatment methods and preventive measures)
Analysis of current transformer open circuit hazards, causes, phenomena, treatment methods and preventive measures
Abstract: in recent years, with the continuous development of power grid and the increase of electrical equipment, the accidents caused by current transformers have also increased, especially the accidents caused by the open circuit of current transformers. The fault and abnormal operation of current transformer will cause maloperation or refusal of protection, so it is very important for field operators to correctly judge the faults of current transformer and deal with it in time. In this paper, the harm, causes, phenomena, treatment methods and preventive measures of current mutual inductance open circuit are briefly analyzed.
Key words: current transformer; open circuit; phenomenon; reason; treatment method; preventive measures
In order to ensure the safe and economical operation of power system, the operation of power equipment must be monitored and measured. But direct access to measurement and protection device is not generally a high voltage equipment, current transformer is the role of the current of the system into small current scaling, supply measuring and protection device, and two times with high voltage isolation system.
I. harm of open circuit of current transformer
The primary current of the current transformer is independent of the current of the two load. When the transformer is working normally, because the impedance is very small and close to the short-circuit state, the magnetization force produced by the primary current is compensated by the two current, the total flux density is not big, and the two winding potential is not big. When the current transformer opens, the impedance Z2 increases infinitely, the two winding current equals zero, and the magnetizing force of the two winding equals zero, and the total magnetization equals the magnetizing force of the primary winding (I0N0=I1N1). It is a completely into the current excitation current, electromotive force is very high in the two winding, the peak of up to several thousand volts, the risk of personal safety, or cause instrument, protection device, transformer insulation damage two. In addition, the magnetic force of the primary winding increases the magnetic flux density of the iron core, which may cause severe overheating of the core.
Two 、 reasons for open circuit of current transformer
There are many reasons for the open circuit of current transformer, and the following are the main points:
1. AC circuit circuit in the experimental wiring terminal, because of the structural and quality defects, in operation, screw and copper screw hole contact bad, cause open circuit.
Test terminal 2. in the current loop connecting sheet, since the connecting piece of wood glue is too long, rotating terminal
metal sheet does not press on the metal connecting sheets on the wrong pressure in the bakelite sleeve, resulting in open.
3., repair work mistakes, such as forget to relay the internal contacts, or mistakenly open the current transformer two circuit, or after the current transformer body test did not connect the two line to zero.
4., the two line terminal contact pressure is not tight, the circuit current is very large, heating, burning or overheating caused by open circuit.
5., two circuit excessive terminal oxidation, loose.
6. outdoor terminal box and junction box are damp, terminal screws and gaskets are too rusty, bad contact or open circuit.
Three, the phenomenon of the current transformer open circuit
When the two circuit of the current transformer is open, the following phenomena are produced for different circuits:
1. by the negative sequence current and zero sequence current start relay protection and automatic device move frequently, but not necessarily to trip (as well as other conditions, may be locked up) protection relay (some with two circuit locking function).
2., the active and reactive power meter indicator is not normal, the three-phase indicator of the ammeter is inconsistent, the meter is not normal.
3. monitoring system related data display abnormal.
The 4. current transformer has a "hum" abnormal sound.
5., the open circuit fault point sparks, discharge sound, smoke and charred phenomenon, abnormal high voltage occurs at the fault point.
The 6. current transformer has a serious fever, accompanied by peculiar smell, discoloration and smoke.
7. maloperation or refusal of relay protection and automatic device.
8. instrument, ammeter, relay and so on smoke burn out.
Four 、 current transformer open circuit processing method
1., when the current transformer two circuit open, first of all to prevent the two winding open circuit, and endanger equipment and personal safety.
After opening the two circuit of the 2. current transformer, it should find out the open circuit position and try to make the short circuit at the open circuit. If there is no short-circuit treatment, the power failure can be applied to the dispatcher. In the process of short circuit handling, attention must be paid to safety, attention should be paid to the two circuit of open circuit with abnormal high voltage. Insulated gloves should be worn, and qualified insulating tools
should be used, under strict supervision.
3., the current transformer two open circuit, should first distinguish the fault, which group is the current circuit, open circuit phase, whether the impact on the protection. Report scheduling, disable protection that may malfunction.
4. minimize the primary load current. If the current transformer is seriously damaged, the load shall be shifted and the power failure shall be checked and dealt with.
5. try to short-circuit the current transformer two times on the test terminal nearby, then check the open circuit point. Short connection shall be used when short circuited and shall be carried out as per drawing. Short contact shall be made in the first circuit of the open circuit where the proper position is taken.
6. if short contact found spark, short connection is effective. The fault point is in the loop below the short contact and can be further searched. If there is no spark in the event of short connection, it may be short circuited. The fault point may be in the loop below the short contact, and the short contact point can be shifted forward to reduce the range.
7. within the scope of the fault, should be able to check the vulnerable terminals and components, check the circuit has touched parts of work.
8., to check out the fault, can handle (such as wiring terminals and other external components loose, bad contact, etc.), can
be immediately processed, and then put into the exit of protection. Failure to handle the faults (such as internal faults of the relay) or fail to find out the faults shall be reported to the higher authorities for inspection, handling, or reverse operation to transfer the load and check the power failure.
Five, preventive measures
1., good quality equipment, equipment procurement, acceptance and other aspects strictly in accordance with relevant regulations, to ensure that the equipment in good condition, and meet quality requirements.
2. operating personnel should strengthen the daily and special period of the equipment (high temperature, high load, bad weather and other inspection and supervision work), through listening, watching, smell and other methods to detect abnormal current transformer, prevent the open to find the cause of the accident is not timely.
3. do the maintenance work in maintenance work in strict accordance with the relevant rules, strengthen the inspection work of maintenance process and maintenance, to prevent the open circuit current transformer due to the maintenance and repair work in the process of negative omission.
4., do a good job in station operators training, often do some targeted anti accident drills and accident expectations, and constantly improve their skills and ability to deal with accidents.
Six, Epilogue
The current transformer is main equipment of power system, but its running status is directly related to the safe operation of power system. In particular, the current transformer two open, if that is not timely or properly, can easily cause equipment and was forced to disable (misoperation and misoperation) accidents, so it is necessary to know and master the open circuit of current transformer, damage phenomenon and treatment of reason and preventive measures, can help us in in the future, when the occurrence of similar abnormalities, can timely and accurately find the point and the successful handling of the accident.
(article from: Changsha loan )