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零序电流故障防范
1. 负荷不平衡引起的零序电流
Zero sequence current caused by 1. load imbalance
为保证配变的安全运行，应采取有效措施抑制零序电流的产生。因中性线不平衡电流是零序电流的3倍，因此，中性线电流的限制值经过理论计算可以证明：联结组为Y，ynO的变压器，其中性线电流不得超过变压器组联结额定电流的25%。这就是抑制零序电流的中性线电流的限制值。
In order to ensure the safe operation of distribution transformer, effective measures should be taken to restrain the occurrence of zero sequence current. Because the unbalanced current of the neutral line is three times that of the zero-sequence current, the limiting value of the neutral line current can be proved by theoretical calculation: the transformer connected with Y, ynO, in which the neutral line current must not exceed 25% of the rated current of the transformer group. This is the limiting value of neutral line current to inhibit zero sequence current.
在配变以三相四线制供电运行中，为抑制零序电流的产生，必须经常检测中性线的电流值，如检测到中性线电流达到或超过额定电流的25%时，这将预示着零序电流的产生。为此，应采取措施对配电网的i相用电负荷进行调整，使三相负荷尽量趋于平衡，以减少中性线电流，抑制零序电流的产生。
In the operation of three-phase four-wire distribution transformer, in order to suppress the generation of zero-sequence current, it is necessary to detect the current value of neutral line frequently. If the current of neutral line reaches or exceeds 25% of the rated current, this will indicate the generation of zero-sequence current. Therefore, measures should be taken to adjust the phase I load of distribution network so as to balance the three-phase load as far as possible, so as to reduce the neutral line current and restrain the generation of zero sequence current.
对于以三相网线制供电的配电变压器，在供用电管理中，首要的工作即是经常检测调整三相负荷，使三相负荷尽量保持基本平衡，保证变压器处于i相负荷平衡的状态运行这不仅可抑制零序电流的产生，而且，也是配变安全、经济运行的有效措施。
In the power supply and consumption management of distribution transformer supplied by three-phase network line, the first task is to detect and adjust three-phase load regularly so as to keep the basic balance of three-phase load as far as possible and ensure that the transformer is in the state of I-phase load balance. This not only can restrain the generation of zero-sequence current, but also is safe and economical for distribution transformer. Effective measures for economic operation.
2. 短路故障引起的零序电流
2. zero sequence current caused by short circuit fault
零序电流保护一般使用在有条件安装零序电流互感器的电缆线路或经电缆引出
Zero-sequence current protection is generally used in cable lines with conditional installation of zero-sequence current transformers or through cable.
继电器的架空线路上。当在电缆出线上安装零序电流互感器时，其一次侧为被保护电缆的三相导线。铁心套在电缆外，其二次侧接零序电流继电器。当正常运行或发生相间短路时，一次侧电流为零，二次侧只有因导线排列不对称而产生不平衡电流。当发生一相接地时，零序电流反映到二次侧，并流入零序电流继电器，使其动作发出信号。
Relays on overhead lines. When the zero-sequence current transformer is installed on the cable outlet line, the primary side of the zero-sequence current transformer is a three-phase conductor of the protected cable. The core is sleeved outside the cable and its secondary side is zero sequence current relay. When normal operation or phase-to-phase short circuit occurs, the primary side of the current is zero, and the secondary side of the unbalanced current only due to the asymmetric arrangement of conductors. When a phase-to-ground fault occurs, the zero-sequence current is reflected to the secondary side and flows into the zero-sequence current relay to signal its operation.
在安装零序电流保护装置时，应特别注意的是：电缆头的接地线必须穿过零序电流互感器的铁心。这是由于被保护电缆发生一相接地时，全靠穿过零序电流互感器铁心的接地线通过零序电流起到作用，否则互感器二次侧也就不能感应出电流，因而继电器也就不可能动作。
When installing zero sequence current protection device, special attention should be paid to: the grounding wire of cable head must pass through the core of zero sequence current transformer. This is because when the protected cable is grounded in one phase, the ground wire which passes through the core of the zero-sequence current transformer acts through the zero-sequence current. Otherwise, the secondary side of the transformer can not sense the current, so the relay can not operate.
配电变压器配置零序保护，最好能就近安装，如果安装在变压器小室。CT二次电缆短，二次负载电阻小，在出u短路时CT不容易饱和，一次电流按比例变为二次电流，有利于零序保护的正确零序保护动作。
Zero sequence protection is suitable for distribution transformers, preferably installed nearby, if installed in transformer room. CT secondary cable is short, secondary load resistance is small, out of U short circuit CT is not easy to saturate, the primary current in proportion to the secondary current, is conducive to the correct zero sequence protection action.
对于城市而言，主城区部分，35kv、10kV系统由于电缆出线日益增多，电缆在发生单相接地故障后，如果不及时切除，易扩大事故，因此，建议新建变电站应采用电阻接地方式，边缘地区新建35 kv、10 kv系统宜采用电阻接地方式，郊区农村地区35 kv和10kV架空配电线路宜采用消弧线圈自动补偿接地方式 。
As for the city, the 35 kV and 10 kV power systems in the main urban area are more and more cable outlets. If the cables are not cut off in time, the accidents will be easily enlarged. Therefore, it is suggested that the resistance grounding method should be adopted in the new substations and the resistance grounding method should be adopted in the new 35 kV and 10 kV power systems in the fringe areas. The 35 kV and 10kV overhead distribution lines in suburban rural areas should adopt arc suppression coil automatic compensation grounding mode.
Zero sequence current caused by 1. load imbalance
为保证配变的安全运行，应采取有效措施抑制零序电流的产生。因中性线不平衡电流是零序电流的3倍，因此，中性线电流的限制值经过理论计算可以证明：联结组为Y，ynO的变压器，其中性线电流不得超过变压器组联结额定电流的25%。这就是抑制零序电流的中性线电流的限制值。
In order to ensure the safe operation of distribution transformer, effective measures should be taken to restrain the occurrence of zero sequence current. Because the unbalanced current of the neutral line is three times that of the zero-sequence current, the limiting value of the neutral line current can be proved by theoretical calculation: the transformer connected with Y, ynO, in which the neutral line current must not exceed 25% of the rated current of the transformer group. This is the limiting value of neutral line current to inhibit zero sequence current.
在配变以三相四线制供电运行中，为抑制零序电流的产生，必须经常检测中性线的电流值，如检测到中性线电流达到或超过额定电流的25%时，这将预示着零序电流的产生。为此，应采取措施对配电网的i相用电负荷进行调整，使三相负荷尽量趋于平衡，以减少中性线电流，抑制零序电流的产生。
In the operation of three-phase four-wire distribution transformer, in order to suppress the generation of zero-sequence current, it is necessary to detect the current value of neutral line frequently. If the current of neutral line reaches or exceeds 25% of the rated current, this will indicate the generation of zero-sequence current. Therefore, measures should be taken to adjust the phase I load of distribution network so as to balance the three-phase load as far as possible, so as to reduce the neutral line current and restrain the generation of zero sequence current.
对于以三相网线制供电的配电变压器，在供用电管理中，首要的工作即是经常检测调整三相负荷，使三相负荷尽量保持基本平衡，保证变压器处于i相负荷平衡的状态运行这不仅可抑制零序电流的产生，而且，也是配变安全、经济运行的有效措施。
In the power supply and consumption management of distribution transformer supplied by three-phase network line, the first task is to detect and adjust three-phase load regularly so as to keep the basic balance of three-phase load as far as possible and ensure that the transformer is in the state of I-phase load balance. This not only can restrain the generation of zero-sequence current, but also is safe and economical for distribution transformer. Effective measures for economic operation.
2. 短路故障引起的零序电流
2. zero sequence current caused by short circuit fault
零序电流保护一般使用在有条件安装零序电流互感器的电缆线路或经电缆引出
Zero-sequence current protection is generally used in cable lines with conditional installation of zero-sequence current transformers or through cable.
继电器的架空线路上。当在电缆出线上安装零序电流互感器时，其一次侧为被保护电缆的三相导线。铁心套在电缆外，其二次侧接零序电流继电器。当正常运行或发生相间短路时，一次侧电流为零，二次侧只有因导线排列不对称而产生不平衡电流。当发生一相接地时，零序电流反映到二次侧，并流入零序电流继电器，使其动作发出信号。
Relays on overhead lines. When the zero-sequence current transformer is installed on the cable outlet line, the primary side of the zero-sequence current transformer is a three-phase conductor of the protected cable. The core is sleeved outside the cable and its secondary side is zero sequence current relay. When normal operation or phase-to-phase short circuit occurs, the primary side of the current is zero, and the secondary side of the unbalanced current only due to the asymmetric arrangement of conductors. When a phase-to-ground fault occurs, the zero-sequence current is reflected to the secondary side and flows into the zero-sequence current relay to signal its operation.
在安装零序电流保护装置时，应特别注意的是：电缆头的接地线必须穿过零序电流互感器的铁心。这是由于被保护电缆发生一相接地时，全靠穿过零序电流互感器铁心的接地线通过零序电流起到作用，否则互感器二次侧也就不能感应出电流，因而继电器也就不可能动作。
When installing zero sequence current protection device, special attention should be paid to: the grounding wire of cable head must pass through the core of zero sequence current transformer. This is because when the protected cable is grounded in one phase, the ground wire which passes through the core of the zero-sequence current transformer acts through the zero-sequence current. Otherwise, the secondary side of the transformer can not sense the current, so the relay can not operate.
配电变压器配置零序保护，最好能就近安装，如果安装在变压器小室。CT二次电缆短，二次负载电阻小，在出u短路时CT不容易饱和，一次电流按比例变为二次电流，有利于零序保护的正确零序保护动作。
Zero sequence protection is suitable for distribution transformers, preferably installed nearby, if installed in transformer room. CT secondary cable is short, secondary load resistance is small, out of U short circuit CT is not easy to saturate, the primary current in proportion to the secondary current, is conducive to the correct zero sequence protection action.
对于城市而言，主城区部分，35kv、10kV系统由于电缆出线日益增多，电缆在发生单相接地故障后，如果不及时切除，易扩大事故，因此，建议新建变电站应采用电阻接地方式，边缘地区新建35 kv、10 kv系统宜采用电阻接地方式，郊区农村地区35 kv和10kV架空配电线路宜采用消弧线圈自动补偿接地方式 。
As for the city, the 35 kV and 10 kV power systems in the main urban area are more and more cable outlets. If the cables are not cut off in time, the accidents will be easily enlarged. Therefore, it is suggested that the resistance grounding method should be adopted in the new substations and the resistance grounding method should be adopted in the new 35 kV and 10 kV power systems in the fringe areas. The 35 kV and 10kV overhead distribution lines in suburban rural areas should adopt arc suppression coil automatic compensation grounding mode.
