For most of the definitions of this standard, see Chapter 2 of GB/T 14048.1--2000 and GB/T 2900.18. For the purposes of this standard, the following additional definitions should be used:
2.15.2 Service short-circuit breaking capacity The service short-circuit breaking capacity shall be in accordance with the conditions specified in the specified test procedure, including the breaking capacity of the circuit breaker to carry its rated current capacity continuously.
2.16 The opening time of the opening time GB/T 1 4048.1-2000 applies and is supplemented as follows:
– For circuit breakers that act directly, the moment the disconnection begins is when the current increases enough to cause the circuit breaker to begin operating.
- For a circuit breaker that operates with any auxiliary power supply, the instant at which the disconnection begins is the instant at which the auxiliary power supply is applied to the disconnected trip.
Note: For circuit breaker, the "off time" is often referred to as the "trip time". Strictly speaking, the trip time is the time between the instant when the disconnection operation starts and the moment the disconnection command becomes irreversible. .
2.17 over-current protective co-ordination
2.5.22 applies in GB / T 14048.1-2000.
2.17.1 Over-current discrimination 2.5.23 applies to GB/T 14048.1-2000.
2.17.2 Total selectivity (total selectivity) In the case of two series-connected overcurrent protection devices, the protection device on the load side performs selective overcurrent protection without causing the protection device to operate.
2.17.3 partial selectivity (partial selectivity) In the case of two overcurrent protection devices connected in series, the protection device on the load side carries out protection at a specified overcurrent level without causing the operation of another protection device. Current selective protection.
2.17.4 Selective limiting current (I?) selectivity current limiting device
Selective current limiting device refers to the current-time characteristic of the total time-current characteristic of the load-side protection device intersecting the pre-arcing time-current characteristic (referring to the fuse) or the tripping-current characteristic (referring to the circuit breaker) of other protection devices.
Selective current limiting device (see Figure A1) is a current limit:
Once below this value, if there are two series overcurrent protection devices, the load side protection device completes its breaking action in time to prevent another protection device from starting to operate (that is, to ensure selectivity);
- Above this value, if there are two series overcurrent protection devices, the load side protection device may not complete its breaking action in time to prevent the other protection device from starting to operate (that is, selectivity is not guaranteed).
2.17.5 Backup protection back-up protection 2.5.2 4 applies in GB/T 14048.1-2000.
2.17.6 Handover current (IH) Take-over current GB/T 14048.1-2000 where 2.5.25 applies and is supplemented as follows:
For the purpose of this standard, 2.5.2 5 in GB/T 14048.1-2000 applies to two over-current protection devices connected in series with the disconnection time of 0.05 s.
For disconnection time <0.05s, two series overcurrent devices can be considered as cooperation. See Appendix A. Note: The crossover current refers to the maximum breaking time between two series-connected overcurrent protection devices and the current coordinates where the current characteristics intersect. .
2.18 IZt characteristics of a circuit breaker Izt characteristic of a circuit-breaker indicates the maximum value of the Izt associated with the breaking time as a function of the expected current (AC symmetry rms value) (usually a curve). The expected current can reach the maximum value. The expected current is the expected current corresponding to the rated short-circuit breaking capacity and the associated voltage.
2.15.2 service short-circuit breaking capacity
The conditions specified in the prescribed test procedures include the ability of the circuit breaker to continuously carry its rated current capability.
2.16 The opening time 2.5.39 of the opening time GB/T 1 4048.1-2000 applies and is supplemented as follows:
– For circuit breakers that act directly, the moment the disconnection begins is when the current increases enough to cause the circuit breaker to begin operating.
- For a circuit breaker that operates with any auxiliary power supply, the instant at which the disconnection begins is the instant at which the auxiliary power supply is applied to the disconnected trip.
Note: For circuit breakers, the "off time" is often referred to as the "trip time". Strictly speaking, the trip time is the time between the instant when the disconnection operation starts and the moment the disconnection command becomes irreversible. .
2.17 Over-current protective co-ordination 2.5.22 applies in GB / T 14048.1-2000.
2.17.1 Over-current discrimination 2.5.23 applies to GB/T 14048.1-2000.
2.17.2 total selectivity total discrimination (total selectivity)
In the case of two series-connected over-current protection devices, the over-current selective protection of the protection device on the load side does not result in the operation of the other protection device.
2.17.3 Local Selective Partial discrimination (partial selectivity)
In the case of two overcurrent protection devices in series, the load-side protection device performs selective protection at a predetermined overcurrent level without causing overcurrent protection of the other protection device.
2.17.4 Selective limiting current (I?) selectivityl imitcu rrent
Selective limiting current refers to the current-time characteristic of the total time-current characteristic of the load-side protection device intersecting the pre-arcing time-current characteristic (referring to the fuse) or the tripping-current characteristic (referring to the circuit breaker) of other protection devices.
Selective current limiting device (see Figure A1) is a current limit:
Once below this value, if there are two series overcurrent protection devices, the load side protection device completes its breaking action in time to prevent another protection device from starting to operate (that is, to ensure selectivity);
- Above this value, if there are two series overcurrent protection devices, the load side protection device may not complete its breaking action in time to prevent the other protection device from starting to operate (that is, selectivity is not guaranteed).
2.17.5 Backup protection back-up protection 2.5.2 4 applies in GB/T 14048.1-2000.
2.17.6 Handover current (IH) Take-over current GB/T 14048.1-2000 where 2.5.25 applies and is supplemented as follows:
For the purpose of this standard, 2.5.2 5 in GB/T 14048.1-2000 applies to two over-current protection devices connected in series with the disconnection time of 0.05 s.
For disconnection time <0.05s, two series overcurrent devices can be considered as cooperation. See Appendix A. Note: The crossover current refers to the maximum breaking time between two series-connected overcurrent protection devices and the current coordinates where the current characteristics intersect. .
2.18 IZt characteristics of a circuit breaker Izt characteristic of a circuit-breaker indicates the maximum value of the Izt associated with the breaking time as a function of the expected current (AC symmetry rms value) (usually a curve). The expected current can reach the maximum value. The expected current is the expected current corresponding to the rated short-circuit breaking capacity and the associated voltage.