Guodian Nanzi Comprehensive Protection PST693U transformer Protector
1 Principle description
1.1 Three section composite voltage overcurrent protection
When the current of any phase is greater than the fixed value and the composite voltage is started, the device will trip after delay.
Function of complex voltage starting element: phase A current is started by Uab, Uca or negative sequence voltage, and phase B current is started by Uab, Ubc or negative sequence voltage,
Phase C current is started by Ubc, Uca or negative sequence voltage. If the re voltage starting element exits, the over-current protection does not need re voltage starting.
1.2 Two section definite time negative sequence overcurrent protection
When the negative sequence current is greater than the fixed value, the device will act after delay. Generally, the first section is used for tripping and the second section is used for alarm.
1.3 Fixed time zero sequence overcurrent protection at HV side
The measurement range of fixed time zero sequence overcurrent at HV side is 0.05~30A (secondary value), which is used for indirect grounding system.
When 3I0 at the high voltage side of the transformer is greater than the fixed value, the device will trip or send a signal after a delay.
1.4 Fixed time zero sequence overcurrent protection at low-voltage side
The measurement range of fixed time zero sequence overcurrent protection at low-voltage side is 0.2~100A (secondary value), which is used for directly grounded system.
When the transformer low zero sequence 3I0 overcurrent is greater than the fixed value, the device will trip or send a signal after a delay.
1.5 Inverse time limit zero sequence overcurrent protection at low-voltage side
The measurement range of inverse time zero sequence overcurrent protection at low-voltage side is 0.2~100A (secondary value), which is used for directly grounded system.
1.6 Overload protection
When the current of any phase is greater than the fixed value, the device will trip or send a signal after delay.
1.7 Overvoltage protection
When any line voltage is greater than the fixed value, the device will trip after delay.
1.8 Low voltage protection
When the voltage of three lines is less than the fixed value, the device will trip after time delay.
Low voltage action condition: if one of the three line voltages is greater than 80V and the delay is 100ms, it is considered that the low voltage action condition is always effective.
After low-voltage action, the low-voltage action condition will automatically become invalid after a delay of 10s. This condition can be enabled or disabled.
1.9 Non electric quantity protection
The device is equipped with 4 non electric quantity protections, each of which can be set as tripping, signaling or exiting. If it is not used as non electricity protection, it is set as exit
These points can be used as normal input.
1.10 PT disconnection alarm
The device uses two methods to identify PT disconnection.
Method 1: When the difference between the larger and smaller voltages of the three lines is greater than 30V, delay for 3s and send PT disconnection signal; When the three line voltages are compared
The difference between large and small is less than 30V, and Uab is greater than 80V, PT disconnection signal returns.
Method 2: When the voltage changes suddenly and the current does not change suddenly, the PT is considered to be disconnected and a PT disconnection signal is sent.
Voltage jump: 100 mS The voltage of any of the three internal lines changes from more than 90V to less than 60V.
No sudden change of current: Ia and Ic are greater than 0.2A, and the change is less than 0.1A.
The three line voltages are greater than 90V, and the PT disconnection signal returns.
1.11 F-C locking function
When any of the three-phase current IA, IB and IC of the transformer is greater than the fixed value of FC locking current, all tripping contacts will be locked after FC locking delay
The protective element of the fuse to ensure that the fuse is fused first. When three-phase current IA, IB and IC are all less than FC blocking current setting, after 100ms
Delay, open the protection element of tripping contactor.
2.13 4-20mA DC output (optional)
The device terminals (3X2, 3X3) output a 4-20mA DC for connecting to the analog quantity acquisition card (AI) of the DCS system.
The DC output can be set as Ia or Uab or P by the user.
