plc program
The so-called "jump" means when the breaker is, because the control switch is not reset or control switch contact device, automatic contact stuck, resulting in tripping control circuit is connected while still tripping, so the circuit breaker will repeatedly to "jump", we call this phenomenon as "jump". Jump protection is the use of the operating … Continue reading What is called anti jump blocking protection?
When the protective earthing of electrical equipment shell with a collision, the earth resistance than the midline of the resistance is large, after the ends of the earth and the formation of shell lining, are not enough to make the short circuit power supply automatic switch and insurance action, and grounding power, and the power … Continue reading In three-phase four wire system, why not allow a part of the equipment to connect to zero, and another part of the equipment used to protect the ground?
A, when the power station and the system and the occurrence of anomalies and accidents, such as the current impulse voltage drop system oscillation, over load, swing swing. Ground and switch automatic tripping, etc.) on duty to do the following work:Check the signal drop down the situation;Check sound, light signal issued;Check the automatic tripping of … Continue reading Relay protection in the abnormal fault, the duty personnel are allowed to what responsibility?
① to inspect if there is no obvious failure, transmission;② Determining human malfunction, caused transformer protection switch tripped or contact the master scheduling system failures, causing the overcurrent protection and transformer oil switch tripping you can check immediately.
DC bus voltage is too high, the long-term running of the electrical components, such as the meter relay, light and so on are easily damaged due to overheating. And when the voltage is too low, it is easy to make the protection device malfunction or reject. General provisions of the allowable voltage change range is … Continue reading DC bus voltage is too high or too low to have any effect?
Drop signal not generally used to reflect the light plate and the alarm, which is characterized in that all the control loop, any signal is not restored, can emit light signal, to remind the personnel on duty or the operator according to the signal to find fault, not omission or false.
The central signal device has two kinds of accident signal and warning signal. The use of the accident signal is that when the circuit breaker is tripped, the circuit breaker can be used to send out the sound of the buzzer immediately, and the circuit breaker indicator lamp is flashing. The warning signal uses: in … Continue reading Central signaling device there are several? What is the use?
AC and DC circuit is not combined with a cable, the main reason is that the AC or DC loop are independent of the system, when a combination of AC and DC cables, AC and DC interfering each other, the insulation resistance of the DC current is reduced; at the same time, insulation system, and … Continue reading AC, DC circuit can apply a cable?
In order to achieve selectivity of over current protection should be the segments of the line protection operation principle of time steps to setting, that is from the power source nearer the end time is longer. Each differential of time is 0.5 seconds. Relay operation time and short-circuit current is independent of the size. Period … Continue reading What is the time limit? What is the counter time limit?
Selection of Megger, mainly is to select the voltage measuring range, high-voltageelectrical equipment required to use the high voltage megohmmeter. Low-voltage electrical equipment using low voltage ohmmeter. General principles are: electrical equipment selection of 500 kV 500~1000-Volt megohmmeter; vases, straps, switch should be used more than 2500 v Megger.Megger measuring range selection principles are: to … Continue reading How to choose the European table?
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