Function Block - ABB 615 series Technical Manual

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1MAC059074-MB A

615 series ANSI

Technical Manual

Function block

GUID-C3405080-34F8-466A-8C2F-214B852164EE V1 EN

Function block

Functionality

A small percentage of ground faults have a very large impedance. They are comparable to

load impedance and consequently have very little fault current. These high-impedance

faults do not pose imminent danger to power system equipment. However, they are a

substantial threat to humans and properties; people can touch or get close to conductors

carrying large amounts of energy.

ABB has developed a patented technology (US Patent 7,069,116 B2 June 27, 2006, US

Patent 7,085,659 B2 August 1, 2006) to detect a high-impedance fault.

The high-impedance fault detection function HIZ also contains a blocking functionality.

It is possible to block function outputs, if desired.

HIZ is limited to be used in 60 Hz electrical networks with efficiently

grounded or isolated neutral.

Operation principle

The function can be enabled and disabled with the Operation setting. The corresponding

parameter values are "Enable" and "Disable".

HIZ uses a multi-algorithm approach. Each algorithm uses various features of ground

currents to detect a high-impedance fault.

Although the HIZ algorithm is very sophisticated, the setting required to operate the

function is simple. The Security Level setting, with the setting range of 1 to 10, is set to

strike a balance between the extremes of security and dependability which together

constitute the reliability of any system. The setting value "10" is more secure than "1".

The higher the Security Level setting, the lower the probability of false detection, but the

system might miss out some genuine fault. On the other hand, a lower setting would make

the system operate more dependably for high-impedance faults in the line, but the

operation is more likely for other transients in the system. There are events in electrical

Protection related functions

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