PST648U Reactor Protection and Control Device

SPG Nanjing PST648U Reactor Protection and Control Device

1 Overview
The PST 648U Reactor Protection and Control Device provides differential protection, backup protection, and non-electrical protection functions, suitable for reactors with voltage levels below 110KV.
1.1 Protection Function Configuration
1) Differential instantaneous protection;
2) Percentage differential protection;
3) TA disconnection detection;
4) Two-stage overcurrent protection;
5) Overload protection;
6) 4 channels of non-electrical protection.
1.2 Control and Monitoring Function Configuration
1) 14 channels of external switch input for telemetry acquisition (expandable to 22 channels);
2) Circuit breaker position, manual tripping, and accident telemetry;
3) Normal remote control of circuit breaker opening and closing;
4) 2 channels of pulse input, electric energy accumulation;
5) GPS time synchronization input (adaptive to minutes and seconds).

2 Technical Parameters

2.1 Operating Range of Protection Components

Phase current: 0.04IN to 20IN

2.2 Setting Error of Protection Components

Current component: ≤±2.5% or ±0.01IN;

Time component: Definite time ≤ (1% setting) + 40ms,

Inverse time ≤±5%(1－I/80IB) or ±20ms, where I is the operating current and IB is the reference current.

Note: UN is the rated value, the same below.

2.3 Overall Operating Time of Protection

Differential instantaneous: At 1.5 times the setting value, not more than 35ms;

Differential protection: At 1.5 times the setting value, not more than 35ms.

3 Protection Functions and Principles

Input 2X:1 is the hard压板 for reactor differential instantaneous and percentage differential protection. After the reactor's total output operates, it outputs 3 pairs of contacts, respectively

(X6:3,X6:7), (X5:5,X5:6), (X5:7,X5:8). When backup protection current and differential protection current are input separately, 1X:17～22 are the backup

protection current input terminals, and the operating parameter control word KG1.10 is set to 0. In this case, the measurement function is for reference only. When backup protection current and differential protection

input current share the same source, the current input terminals are 1X:9～14, and the operating parameter control word KG1.10 is set to 1. In this case, 1X:17～22

are the measurement current input terminals.

3.1 Differential Instantaneous Protection

When the differential current of any phase exceeds the differential instantaneous setting value, it operates the total output relay. It is used to quickly trip the reactor in case of severe

faults within the differential protection zone.

3.2 Percentage Differential Element

It adopts the conventional percentage differential principle, with the operating equations as follows:

Id > Icd (Ir < 0.9Ie)

Id - Icd > Kcd · (Ir - 0.9Ie) (Ir ≥ 0.9Ie)

The percentage differential element operates when both equations are satisfied. Here, Id is the differential current, Ir is the restraining current, Kcd is the

percentage restraining coefficient, Icd is the differential current threshold setting, and Ie is the secondary rated current of the reactor. The differential current threshold should not be too small; it is recommended

to set Icd = (0.4～0.8) Ie. The reactor percentage restraining coefficient Kcd is recommended to be in the range of 0.3～0.7.

3.3 TA Disconnection

When the differential current of any phase exceeds the differential starting current, instantaneous TA disconnection detection will not be performed if any of the following conditions are met:

a. Before starting, the phase current on one side is less than 20% of the rated current on that side, then that side is not judged;

b. After starting, the phase current exceeds 120% of the rated current on that side;

c. After starting, the current on any side increases compared to before starting.

If none of the above three conditions are met, and one side simultaneously satisfies the following conditions after a 9s delay, it is judged as TA disconnection:

a. Only one phase current is zero;

b. The other two phase currents remain unchanged from before starting.

Instantaneous TA disconnection can be configured via the control word to either issue an alarm signal only or to also block the differential protection.

When the differential current exceeds 15% of the differential starting current and persists for more than 10s, an alarm signal is issued and a differential current over-limit report is generated, but the differential protection is not blocked.

This function can also serve as a monitoring function for the AC sampling circuit of the protection device.