①It can integrate main and backup protection functions in one device, with good operational performance;
②It has self-check function, improving the knowability of the device's safe operating condition;
③It has remote communication function, meeting the requirements of automation development;
④Its production and debugging are convenient and standardized, which has improved the device, revolutionized the appearance of traditional protection equipment, and promoted the technological progress of relay protection in China. Its emergence quickly received welcome and attention from operation, design, and manufacturing sectors.
After the successful application of microprocessor-based protection technology in 220KV line distance protection, it was quickly extended to power grids of various voltage levels, and applied to busbar protection, generator and transformer protection, fault recording devices, substation integrated automation systems, and grid security automatic devices. Microprocessor-based protection focuses on improvement during application, inheriting the principles of traditional analog protection, technology, and long-term accumulated operational experience. Anti-interference measures have been strengthened in the device itself and at the operation site. The CPU has developed from initially one to multiple, with the bit width increasing from 8 bits to 32 bits, and subsequently adopting a circuit composed of two high-speed digital signal processing chips (CSP) to meet the requirements of operation capability and speed, and greatly improving anti-interference capability. Therefore, microprocessor-based protection has been rapidly promoted and applied with an unstoppable trend, and has also driven the development of the national microprocessor protection industry. By the end of 1991, 26 power grids and provincial bureaus nationwide used microprocessor-based protection, with 321 sets put into operation; by 2002, among a total of 36,000 relay protection devices in systems of 220KV and above nationwide, microprocessor-based protection reached about 20,000 units, accounting for 56% of the total. Among them, line protection of 220KV and above totaled about 16,000 units, with microprocessor-based protection accounting for about 90%; fault recording devices achieved 99.5% microprocessor-based.
