ABB RELION 620 Series Technical Manual page 613

1MAC504801-IB E
6.5.5
620 series ANSI
Technical Manual
Application
Some protection functions operate on the basis of the measured voltage value in the
protection relay point. These functions can fail if there is a fault in the measuring circuits
between the voltage transformers and protection relay.
A fault in the voltage-measuring circuit is called a fuse failure. This term is misleading
since a blown fuse is just one of the many possible reasons for a broken circuit. Since
incorrectly measured voltage can result in a misoperation of some of the protection
functions, fast failure detection is one of the means to block voltage-based functions
before they operate.
GUID-66F27D13-9297-47BE-90B9-24020B468540 V1 EN
Figure 309: Fault in a circuit from the voltage transformer to the protection relay
A fuse failure occurs due to blown fuses, broken wires or intended substation operations.
The negative sequence component-based function can be used to detect different types of
single-phase or two-phase fuse failures. However, at least one of the three circuits from the
voltage transformers must be intact. The supporting delta-based function can also detect
a fuse failure due to three-phase interruptions.
In the negative sequence component-based part of the function, a fuse failure is detected
by comparing the calculated value of the negative sequence component voltage to the
negative sequence component current. The sequence entities are calculated from the
measured current and voltage data for all three phases. The purpose of this function is to
block voltage-dependent functions when a fuse failure is detected. Since the voltage
dependence differs between these functions, 60 has two outputs for this purpose.
Section 6
Supervision functions
607