1 nominal value
A suitable approximate quantity used to mark or identify a switching device or component, as well as equipment.
2 Limit values
The maximum or minimum allowable value of a quantity in specifications and standards.
3 Rated values
A quantity value generally specified by a manufacturing plant for switch appliances, devices, or equipment under specified working conditions.
4 Quota
A set of rated values and operating conditions.
5 (Expected current of circuits and related switching devices or fuses)
The current that may flow in a circuit when each pole or fuse of a switching device is replaced by a conductor with negligible impedance.
Note: The method used to calculate or represent the expected current is specified in the relevant product standards.
6 Expected peak current
The expected peak current during the transient period after the circuit is turned on.
Note: This definition assumes that the current is connected by an ideal switching device, that is, the impedance instantaneously changes from infinity to zero. For circuits with several current paths,
For example, in a multiphase circuit, this definition further assumes that all poles are simultaneously energized with current, or even only one pole's current is considered.
Expected symmetrical current of 7 (AC circuit)
The expected current at the moment when the transient phenomenon disappears after the AC circuit is connected.
Note: For multiphase circuits, it is expected that the symmetric current will only meet the non transient periodic state on one pole once.
2. The expected symmetrical current is represented by the effective value (r. m.s).
8 (maximum expected peak current of AC circuit)
The expected current peak at the moment when the current begins to occur leading to the maximum possible value.
Note: For multipole appliances in multiphase circuits, only one pole is considered for the maximum expected peak current.
9 (expected current of one pole of a switching device)
The expected current generated when connected under specified conditions.
Note: The specified conditions may be related to the way the expected current is generated, such as using an ideal switching device; Or it is related to the instantaneous expected current it generates, such as the moment that causes the maximum expected current in an AC circuit; Or related to the maximum rate of increase, these conditions are specified in the relevant product standards.
10 (expected breaking current of one pole or fuse of a switching device)
Corresponding to the expected current determined at the beginning of the breaking process.
Note: The provisions regarding the instantaneous breaking process should be provided in the relevant product standards. For mechanical switch appliances and fuses, it is usually the moment when the arc is generated during the breaking process.
11 (Breaking current of switching devices or fuses)
The current value that flows through one pole or fuse of the switching device at the moment of generating an arc during the breaking process.
Note: For AC, the current is represented by the symmetrical effective value of the AC component.
12 (breaking capacity of switching devices or fuses)
The expected breaking current value of a switching device or fuse that can be broken at a specified voltage under specified usage and performance conditions.
Note: 1. The specified voltage and conditions are specified in the relevant product standards.
2. For AC, the current is represented by the symmetrical effective value of the AC component.
3. The short-circuit current breaking capacity is shown in 14.
13 (Switching ability of electrical appliances)
The expected current value at which a switching device can be turned on at the specified voltage under specified usage and performance conditions.
Note: 1. The specified voltage and conditions are specified in the relevant product standards.
2. The short-circuit making ability is shown in 15.
14 Short circuit breaking capacity
The breaking capacity under specified conditions, including short circuits at the output terminals of switchgear.
15 Short circuit making ability
The ability to make connections under specified conditions, including short circuits at the output terminals of switching devices.
16 critical load current
Breaking current with significantly prolonged arc ignition time within the range of usage conditions.
17 critical short-circuit current
The breaking current value of the arc energy is significantly higher than the rated short-circuit breaking capacity, although it is lower than the rated short-circuit breaking capacity.
18 Joule integral (I2t)
The integral of the square of the current over a given time. (441-18-23)
19 cut-off current (allowable current)
The maximum instantaneous current value reached by a switching device or fuse during the breaking action.
Note: When the circuit current has not yet reached the expected peak current, this concept is particularly important when the switch or fuse breaks.
20 time current characteristics
A function curve that represents the pre arc time or melting time as the expected current under specified operating conditions.
21. Cut off current characteristics; Permissible current characteristics
Under specified operating conditions, the cutoff current is a function curve of the expected current.
Note: In communication situations, the cutoff current is the maximum value that can be achieved at any degree of asymmetry. The cutoff current in DC conditions is the maximum value reached at a specified time constant.
Coordination of overcurrent protection for 22 overcurrent protection appliances
Two or more overcurrent protection devices are connected in series to ensure selective overcurrent protection and/or backup protection.
23 Overcurrent selectivity
The coordination of operating characteristics between two or more overcurrent protection devices. When overcurrent occurs within the given range, the device specified to operate within this range will act, while other devices will not act.
Note: There is a difference between series selectivity and network selectivity. Series selectivity includes different overcurrent protection devices passing through the same overcurrent simultaneously; Network selectivity involves the same protective device passing through different sizes of overcurrent.
24 backup protection
A type of overcurrent coordination between two series connected overcurrent protection devices. The power side protective device (usually the power side, but not necessarily the power side) achieves overcurrent protection with/without the help of another protective device and prevents the overload of another protective device.
25 handover current
The current value at the intersection of the time current characteristic curves of two overcurrent protection devices.
26 Short Delay
Intentional time delay for operation within the rated short-term withstand current range.
27 Short time withstand current
The current that a circuit or switch in the closed position can carry within a specified short period of time under specified usage and performance conditions.
28 peak withstand current
The peak current that a circuit or switch in the closed position can withstand under specified usage and performance conditions.
29 (for circuits or switching devices) Limiting short-circuit current
The expected current that a circuit or switching device protected by a specified short-circuit protection device can withstand when the short-circuit protection device operates under specified usage and performance conditions.
Note: For this standard, short-circuit protection devices generally refer to circuit breakers or fuses.
2. The definition extends the concept of current limiting devices to short-circuit protection devices, where the function of short-circuit protection devices is not limited to current limiting effects.
30 (agreed non tripping current of overcurrent relay or release)
The specified current value that a relay or release can carry without action within a specified time (agreed upon time).
31 (Agreed tripping current of overcurrent relay or release)
The specified current value that causes the relay or release to operate within a specified time (agreed upon time).
32 (switchgear) applied voltage
The voltage applied between the two terminals of one pole of the switching device just before the current is connected.
Note: This definition applies to unipolar appliances, while for multipole appliances, the applied voltage refers to the relative phase voltage between the power supply terminals of the appliance.
33 recovery voltage
The voltage that occurs between one pole or two terminals of a fuse in a switching device after breaking the current.
Note: 1. This voltage can be considered as having two consecutive time intervals, during which it is a transient voltage, and only remaining in the subsequent second time interval
Restore voltage or power frequency voltage in steady state.
2. The above definition applies to unipolar appliances, while for multipole appliances, the recovery voltage refers to the relative phase voltage between the power supply terminals of the appliance.
34 transient recovery voltage
Recovery voltage within a time period with significant transient characteristics.
Note: Transient voltage can be oscillating, non oscillating, or a combination of both, depending on the characteristics of the circuit, switching device, or fuse. Transient voltage includes the neutral point voltage offset of multiphase circuits.
35 power frequency recovery voltage
The recovery voltage after the disappearance of transient voltage phenomenon.
36 DC steady-state recovery voltage
The recovery voltage after the transient voltage phenomenon disappears in a DC circuit, if there are ripples, this voltage is expressed as the average value.
37 (expected transient recovery voltage of the circuit)
The transient recovery voltage after the expected symmetrical current is broken by an ideal switching device.
Note: The above definition assumes that all switch devices or fuses with expected transient recovery voltage to be measured are replaced by an ideal switch device, that is, the impedance immediately changes from zero to infinity at zero current (i.e. natural zero crossing). For circuits where current can flow through several different paths, such as multiphase circuits, this definition further assumes that the ideal switch device will only break the current at the considered pole.
38 (peak arc voltage of mechanical switching appliances)
The maximum instantaneous voltage that occurs between the two terminals of one pole of the switching device during the arc ignition period under specified conditions.
39 (Breaking time of mechanical switch appliances)
The time interval between the moment the switching device is disconnected and the moment when all the arc contacts of the poles are separated.
Note: The moment when the disconnection operation begins, i.e. the moment when the disconnection command is issued (such as applying a tripping current, etc.), is specified in relevant product standards.
40 (arc ignition time of one pole or fuse)
The time interval from the moment when an arc occurs at one pole or fuse of the switching device to the moment when the arc in that pole or fuse finally extinguishes.
41 (Arc ignition time of multipole switching appliances)
The time interval from the moment when the first arc is generated to the moment when all pole arcs are finally extinguished.
42 breaking time
The time interval from the moment of disconnection of mechanical switch appliances (or the pre arc time of fuses) to the moment when the arc time ends.
43 Connection time
The time interval from the moment the mechanical switch is closed to the moment the current starts flowing through the main circuit.
44 closing time
The time interval between the start of the closing operation of a switching device and the instant when all the contacts of the poles come into contact.
45 on/off time
For a release that is energized and disconnected at the moment when the current starts to flow in the main circuit, it refers to the time interval from the moment when the current starts to flow in one pole of the switching device to the moment when all pole arcs finally extinguish.
46 Electrical Clearance
The shortest straight-line distance between two conductive components.
Electrical clearance between 47 poles
The electrical gap between any conductive components between adjacent poles.
2.4.48 Electrical clearance to ground
The electrical gap between any conductive component and any grounded component or component used for grounding.
2.4.49 Electrical clearance (open distance) between disconnected contacts
The total electrical gap between the contacts of one pole of a mechanical switch or any conductive component connected to the contacts in the disconnected position
50 (isolation distance of one pole of mechanical switchgear)
The electrical gap between the contacts in the disconnected position when meeting the safety requirements of the isolator.
51 Creepage distance
The shortest distance along the surface of the insulating material between two conductive components.
Note: The joint between two insulation material components is considered as the surface part.
52 working voltage (actual working voltage)
The maximum effective value of AC voltage or maximum DC voltage that may actually occur (locally) at any insulation end under rated power supply voltage.
Note: 1. This definition does not consider transient voltage.
2. Open circuit conditions and normal operating conditions should be taken into consideration.
53 transient overvoltage
A phase to ground, phase to neutral, or phase to phase overvoltage that lasts for a considerable amount of time (a few seconds) at a certain position.
54 transient overvoltage
There are several meanings of transient overvoltage in this standard:
54.1 On Off Overvoltage
Transient overvoltage that occurs at a certain position in the system due to specific on/off operations or faults.
54.2 Lightning overvoltage
Transient overvoltage that occurs at a certain position in the system due to specific lightning discharge (see IE 60060 and GB 311.1).
54.3 Functional overvoltage
Overvoltage consciously applied to meet the functional requirements of electrical appliances.
55 impulse withstand voltage
The highest peak value of the impulse voltage with a certain shape and polarity that does not cause breakdown under specified test conditions.
56 power frequency withstand voltage
The effective value of the power frequency sinusoidal voltage that does not cause breakdown under specified test conditions.
57 Pollution
Any external material condition that can affect the dielectric strength or surface resistivity, such as a solid, liquid, or gas (free gas).
58 (pollution level of environmental conditions)
The classification of environmental conditions based on the magnitude of conductive or hygroscopic dust, free gases or salts, and relative humidity, as well as the frequency of surface dielectric strength and/or resistivity reduction events caused by moisture absorption or condensation.
Note: 1. The pollution level of the exposed device may be different from that of devices in a macroscopic environment that provide a shell or internal heating method to prevent moisture absorption or condensation.
For the purpose of this standard, pollution level refers to the pollution level of the micro environment.
Micro environment of 59 (electrical gap or creepage distance)
According to the surrounding environmental conditions at the considered electrical clearance or creepage distance.
Note: The micro environment of electrical clearance or creepage distance determines its impact on insulation, rather than the environment of the device determining its impact. The micro environment may be better than the device's
The environment may be worse than it. The micro environment includes all factors that affect insulation, such as climate conditions, electromagnetic conditions, and the generation of pollution.
60 (overvoltage category in circuits or electrical systems) (installation category)
The classification is determined based on the expected transient overvoltage generated in the limited (or controlled) circuit (or in electrical systems with different nominal voltages) and the relevant methods used to limit overvoltage.
Note: In an electrical system, switching from one overvoltage category to another lower overvoltage category is achieved by taking measures that meet the requirements of reducing transient overvoltage to
The method of obtaining the required interface values for lower overvoltage categories, such as using overvoltage protectors that can absorb, consume, or convert surge current energy, or series or parallel impedance combinations.
61 Insulation coordination
The insulation characteristics of electrical equipment are related to the expected overvoltage and overvoltage protection device characteristics, as well as the expected micro environment and pollution protection methods.
62 uniform electric field
An electric field where the voltage gradient between electrodes is essentially constant, for example, between two balls, where the radius of each ball is greater than the distance between the two.
63 non-uniform electric field
An electric field with an unstable voltage gradient between electrodes.
64 leakage marks
The process of gradually forming a conductive path on the surface of solid insulation materials under the combined action of electric field and electrolyte.
65 compared to leakage trace index (TI)
The maximum voltage value at which the material can withstand 50 drops of test solution without forming leakage marks. Represented by V.
Note: 1. Each test voltage value and TI should be a multiple of 25.
The above definition is selected from Article 2.3 of GB 4207-1984.