Innovative protection method optimizes safety and power supply quality

ABB has extended its award-winning earth-fault protection portfolio with a new addition: touch voltage-based earth-fault current protection, also known as IFPTOC in IEC 61850 - the international standard that defines communication protocols for intelligent electronic devices in substations.

In a world-first, customers operating compensated distribution networks can now benefit from this new protection method to safeguard human lives and installed assets with minimum impact to the quality of the electricity supply and unnecessary power outages.

The protection method can calculate the fault current, and estimate the resulting hazardous touch voltage, in the actual fault location. It introduces a dynamic operation delay dependent on the calculated fault current and touch voltage level at the fault location. This way the function can satisfy electrical safety codes, such as EN 50522 or IEEE 80, requirements concerning maximum allowed touch voltages, while still avoiding unnecessary supply breaks. This means network operations managers can be reassured that their network is protected according to the prevailing safety code continuously, even under changing network topology or fault conditions.

“The technology is the result of several years of research and development work and close cooperation with our customers," said Ari Wahlroos, Senior Principal Engineer at ABB. “This unique method ensures both dependable and precisely timed protection operation, in compliance with the applied legislation during all possible operating conditions.”

Customers, such as Finnish distribution system operator (DSO) Alva, sees the capability of having earth-fault protection that offers an optimal balance between safety and supply quality. As the first in the world, Alva has ABB’s new protection method already in use.

“The new earth-fault protection method IFPTOC continuously ensures that the electrical safety limits of the network are not exceeded. When the fault is located with trial switchings, IFPTOC calculates and monitors the actual earth-fault current, and changes its operate time, ensuring that we don’t exceed the limits of human tolerance, also during faults. This ensures safe network operation at all times,” said Sakari Kauppinen, Operations Manager at Alva Sähköverkko.

In cooperation with Alva, the reliability of the new protection method has undergone extensive field tests in a live environment at the company’s newest substation in the city of Jyväskylä. With this type of field test, it is possible to validate the correct operation of protection during different earth-fault scenarios.

By taking the new protection method into use, DSOs can confidently enhance electrical safety and ensure supply continuity.

“During the field tests, we ran various fault situations in advance to confirm that the new protection method was working as planned. With the new protection method, we can measure the fault current at the fault location and confirm that the protection function is working in an optimized manner,” said Sakari Kauppinen. ”And we are now upgrading with better protection technology to improve safety in the entire network”.

ABB’s new protection method is available across selected products, including the all-in-one advanced protection relay Relion® REX640.

Source: new.abb.com