Archive for January, 2017

Current and Voltage Transformer Fault Handling Precautions

In the measurement of high current alternating current, in order to facilitate the secondary instrument measurement needs to be converted to a more uniform current (the provisions of the current transformer secondary rated 5A), the other line voltage is relatively high, such as direct measurement is very dangerous. Current transformer to play the role of variable sawing machine current and electrical isolation, current transformer is the step-up (down) transformer.It is the power system measuring instruments, relay protection secondary equipment to obtain information on the primary circuit of the electrical current sensors, current Transformer will be converted to high current proportional to low current, the current transformer primary side in a primary system, the second side of the measurement instruments, such as relay protection.
For the current transformer and voltage transformer failure, the corresponding processing precautions are as follows:
1, the voltage transformer breakdown processing matters needing attention:
If the voltage transformer internal noise and produce smoke, oil leakage and other serious phenomenon, and one side of the high-voltage fuse and not immediately fuse, then disconnect the switch should be avoided to cut off the fault voltage transformer, because at this time the voltage transformer Of the current may be relatively large, in order to prevent the arc generated when the isolation switch. Should find a way to disconnect the circuit breaker on the power supply, and then in the absence of electricity in the state of the voltage transformer isolation switch, especially when the voltage transformer fire, you should first cut off the power, and then use carbon dioxide fire extinguisher or dry Extinguishing.
2, the current transformer failure, should pay attention to the following issues:
(1) the current transformer secondary side in the operation may not open, once the secondary side open, due to excessive iron loss, the temperature is too high and burned, or the secondary winding voltage will be insulation breakdown, the occurrence of high-voltage electric shock Of the risk. So in exchange for the instrument, such as the replacement of ammeter, active form, reactive power meter, etc. should be short circuit before the first exchange of measurement instruments. When the table is scheduled, the first access to the secondary hydraulic hole punch machine circuit and then remove the short wiring and check the meter is normal. If there is a spark in the removal of short wiring, then the current transformer is open, immediately re-shorted to identify the meter circuit does not open the phenomenon, before re-remove the short wiring. In the removal of current transformer short-circuit work, should stand on the insulation pad, the other to consider disabling the current transformer circuit protection device, until the work is completed, before the protection device into operation.
(2) If the current transformer buzzing sound, should check whether the internal core loose, the core bolt can be tightened.
(3) current transformer secondary side of the end of the shell steel fabrication must be reliable grounding. In this case,
(4) When the current transformer secondary side of the coil insulation resistance of less than 10 to 20 megohms, must be dry, so that insulation recovery before use.
When the current transformer-related failures occur, it will directly affect the operation of a system line security, should be promptly reported to the higher authorities and relevant departments in a timely manner cut off the fault current transformer power supply, the fault current transformer is disabled for processing. In the secondary winding open when the approach, according to the actual situation of the site to deal with failure, in accordance with the relevant requirements to take certain security measures before they can be used again.