Tv and ta disconnection of various types of protection devices

Protective Device Models and TV/TA Disconnection Criteria

Various protective devices are used in power systems to detect and respond to faults such as TV (voltage transformer) or TA (current transformer) disconnections. Below is a detailed description of the criteria used by different models:

RCS985

TV Disconnection: If the positive sequence voltage is less than 30V and any phase current is 0.04In, or the negative sequence voltage 3U2 exceeds 8V, a 10-second delay alarm is triggered. The signal resets automatically after 10 seconds once the issue is resolved.

TA Disconnection: If the negative sequence current I2 is greater than 0.2A plus 0.25×Imax, a 10-second delay alarm is issued. The signal returns after the abnormality disappears.

BP2B

TV Disconnection: When the generator terminal voltages from two sets of TV differ by more than 5V for phase-to-phase voltages or 3V for positive sequence voltage, a 0.2s delay alarm is triggered, followed by a TV switch.

TA Disconnection: Only when the differential protection control word is enabled, the differential current alarm is activated. A ratio brake criterion is used for better sensitivity: dI > di_bjzd and dI > kbj × Ires.

RCS931

TV Disconnection: If the three-phase voltage vector sum is over 8V, a 1.25s delay alarm is sent. If the bus PT is used, the same applies if the positive sequence voltage is below 33.3V. If the line PT is used, an alarm is also triggered if any phase flow element operates or the TWJ does not operate.

TA Disconnection: If the self-produced zero-sequence current is less than 0.75 times the external one, or vice versa, a 200ms delay alarm is issued. If there's no zero-sequence voltage but at least one phase has no current, a 10s delay alarm is triggered.

RSC925

TV Disconnection: If the phase-to-phase current variation and zero-sequence current do not operate, and either the three-phase voltage sum is over 12V or the positive sequence voltage is under 33V with any phase current above 0.06In, a 1.25s delay alarm is triggered.

TA Disconnection: If the self-produced zero-sequence current is over 0.1In, a 10s delay alarm is issued. Otherwise, a 10s delay is applied if the zero-sequence current is below 0.1In.

RCS915

TV Disconnection: If the residual voltage of a disconnected phase is below 44V, a 1.25s delay alarm is issued. If all three-phase voltages are below 18V and the bus-tie TA current is above 0.04In, another 1.25s delay alarm is triggered.

TA Disconnection: If a single phase current exceeds 0.06In, or three-phase balanced current exceeds IDX, a 5s delay alarm is issued.

CSC103

TV Disconnection: If the three-phase voltage sum is over 7V, or if any phase voltage is below 8V and current is above 0.04In, a 1.25s delay alarm is triggered.

TA Disconnection: If the zero-sequence current is over the setting for 12s, a CT disconnection alarm is issued, and the zero-sequence protection is blocked.

CSC125A

TV Disconnection: Two criteria are used: 1) Three-phase voltage sum over 7V; 2) All phase voltages below 8V and current over 0.04In. A 1.25s delay alarm is issued.

TA Disconnection: If the zero-sequence current is over the setting for 12s and the disconnected phase current is below 0.06In, a 12s delay alarm is issued. This does not lock the outlet power.

CSC300

TV Disconnection: When two TVs are present, their secondary voltages are compared. If one loses voltage, a 10s delay alarm is issued. For single TV cases, specific voltage and current thresholds are used.

TA Disconnection: If a phase has no current and there’s a differential current, a TA disconnection is assumed. Sudden current changes are also considered.

CSC150

TV Disconnection: In neutral grounding systems, if three-phase voltage is below 8V and branch currents are not all zero, or if 3U0 is over 7V, a 10s delay alarm is triggered.

TA Disconnection: Bus-coupled CT disconnection is detected using differential current imbalances.

WFB800

TV Disconnection: Multiple criteria are used, including voltage balance, zero-sequence voltage, and phase voltage differences. Alarms are delayed between 80ms and 10s depending on conditions.

TA Disconnection: If differential current exceeds 0.15In, a TA disconnection is detected based on current values and consistency.

WXH801

TV Disconnection: Two criteria: 1) Three-phase voltage sum over 7V; 2) Three-phase voltage loss with current thresholds. Both have 1s delays.

TA Disconnection: If zero-sequence current lasts over 12s, a CT disconnection alarm is triggered, and protection is locked until the current disappears.

WMH800

TV Disconnection: In large ground current systems, if any phase voltage is below the threshold or 3U0/3U2 is over 7V, a 7s delay alarm is issued.

TA Disconnection: If differential current exceeds limits for 7s, a CT disconnection is detected.

BP2B

TA Disconnection: If the difference current exceeds a set value, a 9s delay alarm is triggered, and the busbar protection is blocked until the loop is normal.

PSL600

TV Disconnection: When the three-phase voltage sum is below 0.5Un, a 100ms delay flag is set. Protection is blocked for 1.25s.

TA Disconnection: Zero-sequence difference current is used to detect CT disconnection.

DGT801

TV Disconnection: Voltage balance is used to compare two TVs. If pressure difference is over set value, the device locks inter-turn protection.

TA Disconnection: If one phase has no negative sequence voltage, it is judged as TA disconnection.