Overview
Cascading failures are series faults in shunt capacitor banks involving more than one capacitor unit (or even more than one rack). They are characterized by the presence of an unbalanced shunt capacitor bank (SCB) current. However, as the connected power system is much stronger than the SCB rating, any unbalance voltage due to cascading faults inside the capacitor bank is typically not present in the system. The “Shunt capacitor cascading failure protection” function provides protection against cascading faults and has two modes to detect the unbalances.
For more detailed information on “Shunt capacitor cascading failure protection” function, refer to ABB, Relion 670 Series manuals.
To see other supported functions, click here.
Function Identification
| Function description | IEC 61850 identification |
IEC 60617 identification |
ANSI/IEEE C37.2 device number |
| Shunt capacitor cascading failure protection | SCCFPVOC | 2 (I > /U <) | 51 V |
Signals & Setting Parameters
Function block of cascading failure protection
SCCFPVOC Input signals
| SCCFPVOC Input signals | |||
| Name | Type | Default | Description |
| I3P | GROUP SIGNAL | – | Group signal for current input |
| U3P | GROUP SIGNAL | – | Group signal for voltage input |
| BLOCK | BOOLEAN | 0 | Block of function |
| BLKST1 | BOOLEAN | 0 | Block of step 1 |
| BLKST2 | BOOLEAN | 0 | Block of step 2 |
SCCFPVOC Output signals
| SCCFPVOC Output signals | |||
| Name | Type | Description | |
| TRIP | BOOLEAN | General trip signal | |
| TR1 | BOOLEAN | Trip signal from step 1 | |
| TR2 | BOOLEAN | Trip signal from step 2 | |
| START | BOOLEAN | General start signal | |
| ST1 | BOOLEAN | Start signal from step 1 | |
| ST2 | BOOLEAN | Start signal from step 2 | |
| IMEAS | REAL | Measured current magnitude | |
| UMEAS | REAL | Measured voltage magnitude | |
SCCFPVOC (51V) Non group settings (basic)
| SCCFPVOC (51V) Non group settings (basic) | |||||
| Name | Values (Range) | Unit | Step | Default | Description |
| GlobalBaseSel | 1 – 12 | – | 1 | 1 | Selection of one of the Global Base Value groups |
SCCFPVOC (51V) Group settings (basic)
| SCCFPVOC (51V) Group settings (basic) | |||||
| Name | Values (Range) | Unit | Step | Default | Description |
| Operation | Disabled Enabled |
– | – | Disabled | Operation Disabled/Enabled |
| CurrentInput | NegSeq 3*ZeroSeq |
– | – | 3*ZeroSeq | Select current signal which will be measured inside function. Note: Needs to have same value as VoltageInput |
| VoltageInput | -NegSeq -3*ZeroSeq |
– | – | -3*ZeroSeq | Select voltage signal which will be measured inside function. Note: Needs to have same value as CurrentInput |
| l_2nd/l_fund | 10.0 – 50.0 | % | 1.0 | 40.0 | Ratio of second to fundamental current harmonic in % |
| Operation1 | Disabled Enabled |
– | – | Disabled | Operation step 1 Disable/Enable |
| IPickup | 121 – 400 | %IB | 1 | 125 | Pickup current level for step 1 in % of IBase |
| tDef1 | 0.00 – 60.00 | s | 0.01 | 0.50 | Definite time delay of step 1 |
| VDepFact1 | 0.0330 – 0.7075 | – | 0.0001 | 0.0640 | Voltage dependent factor for step 1. Note: it is recommended to be set as [1-(117/I>)], to follow the capacitor impedance |
| HarmRestr1 | Disabled Enabled |
– | – | Disabled | Enable block of step 1 by 2nd harmonic restrain to be used for 3I0 current only |
| Operation2 | Disabled Enabled |
– | – | Disabled | Operation step 2 Disable/Enable |
| pickup2 | 125 – 400 | %IB | 1 | 130 | Pickup current level for step 2 in % of IBase |
| tDef2 | 0.00 – 60.00 | s | 0.01 | 0.50 | Definite time delay of step 2 |
| VDepFact2 | 0.0640 – 0.7075 | – | 0.0001 | 0.1000 | Voltage dependent factor for step 2. Note: it is recommended to be set as [1-(117/I>>)], to follow the capacitor impedance |
| HarmRestr2 | Disabled Enabled |
– | – | Disabled | Enable block of step 2 by 2nd harmonic restrain to be used for 3I0 current only |
SCCFPVOC Monitored data
| SCCFPVOC Monitored data | ||||
| Name | Type | Values (Range) | Unit | Description |
| IMEAS | REAL | – | A | Measured current magnitude |
| UMEAS | REAL | – | kV | Measured voltage magnitude |
Logics & highlights
Cascading failure within SCB
General voltage restrained characteristic for SCB cascading protection (Stage 1 and stage 2)
General voltage restrained characteristic for SCB cascading failure protection (Stage 1 and Stage 2)
Block condition for additional zero sequence 2nd harmonic restrained feature
Logic Diagram of cascading failure protection
