In mines and mines, there is always dust, coal or soil, with a metal content. Outlets of gases - propane, butane and methane are also common. All this creates an explosive and fire hazard when using electrical equipment in underground workings and the impossibility of using conventional household neutral grounding under these conditions, which gives a large spark during an emergency shutdown. Therefore, underground power supply safety is provided by leakage current protection devices with isolated neutral. A short circuit in them occurs to the body and is not accompanied by the occurrence of a discharge arc or sparks.
Machine action
To control the power supply network, a weak direct current is passed through it, which is grounded. With the help of a relay, a bias pulse is sent to the artificial neutral, created from three resistors, in the event that a current leakage occurs. A signal is immediately given to the machine, and the entire system is turned off. This is done so that when the sectors are connected one by one, the bad sector will give a repeated disconnection signal and it could be quickly detected.
Appearance and internal structure of the device
AZUR is designed as a block with dimensions of 177X320X156 mm and weighing about 8 kg. It connects to the distribution system of a mobile transformer in a mine or mine substation. If a leakage current occurs, the device immediately sends a signal to the switch. On the body there are: an alarm panel, contacts for wires, as well as brackets for fixing the unit in the substation cubicle. The metal case contains electrical circuits made on panels and boards. To power the device, a voltage of 127V is required, while it serves a three-phase network 660 /1140V, at a current frequency of 50Hz.
Test & Operation
The microcontroller protection device is undergoing a fourth improved performance. Acceptance tests for this type of apparatus must meet the following requirements:
- carry out the function of self-monitoring of individual circuits of the device;
- measure the parameters of the passing current;
- determine the phase of the current in case of its leakage;
- react to changes in isolation state;
- in case of emergency shutdown, work in locked mode;
- be resistant to false alarms.
All manufactured devices must be checked.
AZUR is designed for operation in a variety of climatic conditions. The temperature regime for it is in the range from -10 to +65 degrees. Shocks, mechanical damage, as well as humidity above 100% and dusty air can adversely affect the operation of the device.
