Grid Security and Stability Control Solutions for Large Industrial and Mining Enterprises
For the need of scale and intensive management, newly built industrial and mining enterprises are often of large scale, thus requiring power grid with the following characteristics:
1. The power supply system of large industrial and mining enterprises shall be connected to the grid of power system by double-circuit or multiple-circuit lines. Some enterprises has one general step-down substation, others may have two general step-down substations. In order to improve power supply reliability, different power supplies will be taken, with the voltage grade ranging from 330/220 kV, 110/66 kV, 35 kV, 10/6 kV, to 0.40 kV
2. For the need of technology and energy saving, industrial and mining enterprises usually have its own power plant and energy conservation units. To meet national energy saving and emission reduction requirements, distributed photovoltaic power station will be constructed close to load center.
3. Large enterprises have more complex loads. They may have one, two, or three kinds of loads, and devices such as generator and transformer. In order to save energy, a variety of motor speed control devices will be applied. Large industrial and mining enterprises have a large number of nonlinear loads, and their daily production and operation have high randomness and impact, with complexly composed harmonic waves from numerous pollutional sources.
4. The power supply system of large industrial and mining enterprises is relatively smaller than the major grid. Its stability is more sensitive to parameters of the system and devices, with lower anti- disturbance ability, i.e. lower flexibility
5. Large industrial and mining enterprises usually have their own power supply system. They can operate either in connection with external power grid or in isolation. Connecting with external power grid can improve reliability but may also bring implicated failures. The relatively complex loads in the factories, the relatively large proportion of large capacity, high frequency, and high density of impact loads, all require highly stable power supply network.
6. To maintain the stability of power grid, all kinds of automatic device are equipped, such as backup power supply automatic switching device, and fast breaking device, but not in a perfect way. There is always lack of coordination between different devices.
7. Large factories and mines tend to focus on production, and pay insufficient attention parameters experiment and management of devices, and the monitoring, maintenance and management of its power supply system.
8. The grid operation management of large industrial and mining enterprises usually takes security and stability as its principle, but seldom gives consideration to the optimization of economical grid operation or emergent solutions for severe accident. In case of severe accident, with limited capacity and network, what key equipments should be secured of power supply?
Because of their special needs for continuous production, large industrial and mining enterprises have high requirements on the safe operation of power grid.
he operation state of the power system can be classified into normal state, alert state, emergency state, out- of- step state, and recovery state. Three Defense Lines can be set, corresponding to various states.
The First Defense Line: fast and reliable relay protection, effective preventive control measures to ensure that the grid can maintain stable operation and power supply in case of common single fault .
The Second Defense Line: use stability control devices and machine-breaking, or load-breaking measures to ensure that the power grid can maintain stable operation in case of serious faults of a lower probability.
The Third Defense Line: set out-of-step splitting, frequency/voltage emergency control devices. In case of multiple severe accidents of a low probability, such devices could prevent the spreading of the accidents and avoid large area blackout.
In case of grid accident, safety and stability system will calculate and decide the number of loads and machines to break according to real-time operation status of the power system, so as to ensure less impact on customers, try to keep systems run in parallel, maintain the security of a certain amount of loads, and protect the safe operation of the main equipments.
Thus, when serious accidents occur in large industrial and mining enterprises, the use of security and stability control system can avoid power break down of the whole factory, ensure continuous power supply of key equipments, and guarantee fast recovery of production.
The grid security and stability control system for large scale industrial or mining enterprise ADVPS-6000/PSCS completely developed by Agent Devote has been put into operation at ENN Energy Holdings Limited in 2014.