Nanjing Nanrui Jibao PCS9613D microcomputer protection device

Nanjing Nanrui Jibao PCS9613D microcomputer protection device

1.2 Device start-up components

The device has set different starting elements for each protective component, and the calculation of protective components can only be carried out after starting. The device has dual sampling capability

Sample technology, the main channel samples data for protection component calculation, and the backup channel samples data for opening the outlet positive power supply. Only starting components

Only when both the protective component and the dual channel sampling data meet the action requirements can the outlet be tripped, otherwise it cannot be tripped.

Differential protection starting element:

The main body of the differential protection starting element is realized by an overcurrent relay that responds to the phase to phase frequency variation, and is also equipped with a relay that responds to the full current

Zero sequence overcurrent relay and phase overcurrent relay complement each other. The principle of each starting component is as follows:

When the following components are activated, differential quick break protection, ratio differential protection, and far trip protection are activated.

Current variation starting element

The starting element that reflects the power frequency variation adopts a floating threshold, and the unbalanced output of the variation during normal operation and system oscillation is balanced

Automatically forming an adaptive threshold, the floating threshold is always slightly higher than the unbalanced output. During normal operation, due to the imbalance

The quantity is small, but the device has high sensitivity.

When the change in phase to phase current exceeds the set value, the starting element will activate.

DIFF>1.25DIFFt+DIFFth formula 1.2-1

among which

DIFF is the change in phase to phase current.

Chapter 3 PCS-9613D Line Fiber Longitudinal Differential Protection Device

62 Nanjing Nanrui Jibao Electric Co., Ltd

DIFFt is a floating threshold that gradually increases automatically as the output of the variable increases. Taking 1.25 times can ensure that the threshold voltage is always slightly higher

Unbalanced output.

DIFFth is a fixed threshold and the starting value for current change.

Zero sequence overcurrent starting element

When both the external and self-produced zero sequence currents are greater than the set value and there is no AC current disconnection, the zero sequence starting element will act.

fd w I I 0 0 >

fd zc I I 0 0 >

Formula 1.2-2

All zero sequence current data are 3I0.

W I0 is the external zero sequence current.

Zc I 0 is the self-produced zero sequence current.

I0 fd is the zero sequence current starting value.

L-phase overcurrent starting element

When the phase current is greater than the set value, the phase overcurrent starting element operates.

IF>IFfd formula 1.2-3

IF is the phase current.

IFfd is the starting value of phase current.

Auxiliary voltage starting component

If a three-phase fault occurs in the area, the current starting element on the weak power supply side may not operate. At this time, if the differential protection on the opposite side is allowed

Signal is used to determine the phase to phase voltage related to the action of the differential current relay. If it is less than 70% of the rated voltage, the auxiliary voltage starting element is activated

action If PT disconnection occurs, the starting component will not operate.

L reclosing starting element

After the reclosing action, open the differential protection for 500ms.

Other protective activation components:

L-phase current starting element

When the three-phase current value is greater than 0.95 times the minimum current setting value, it will act. This starting component is used to activate the corresponding overcurrent protection.

Zero sequence current start

When the zero sequence current is greater than 0.95 times the minimum setting value, it will act. This starting element is used to activate the corresponding zero sequence overcurrent protection.

1.3 Differential protection

The current differential relay consists of three parts: differential quick break relay, ratio differential relay, and differential jump relay.

Please refer to PCS-9611D for other functions of PCS-9613D.

Differential quick break relay

To prevent the ratio differential protection from being delayed due to CT saturation in case of severe short circuit faults in the area, the device is equipped with differential quick break protection,

Used to quickly trip and cut off faults when serious faults occur within the protected area. Differential quick break protection does not require any locking conditions to be set, when any

Instantaneous action when the differential current is greater than the differential speed determination value.

Nanjing Nanrui Jibao PCS9613D microcomputer protection device