The most basic characteristics of a power failure are a rise in current and a drop in voltage. The original principle of relay protection is the characteristic of rapid increase in response current, that is, fuse protection and overcurrent protection. Another feature of the fault is the voltage drop, corresponding to the low voltage protection. At the same time, a parameter that reflects the decrease of voltage and increase of current is impedance, which corresponds to distance protection. It reflects the distance of the fault point by how much the impedance decreases, and determines whether the protection acts or not.
When a short-circuit fault occurs in the power system, many parameters will change, and the parameters with obvious changes are suitable for the judgment basis of protection. Such as:
overcurrent protection - in case of short circuit, the current is higher than normal current;
low voltage protection - in case of short circuit, the bus voltage decreases;
distance protection - in case of short circuit, the measured impedance at the beginning of the line decreases;
direction protection - the difference between voltage and current The change of the phase difference between the relays;
differential protection - when the line is short-circuited, the current phase difference on both sides changes; the
relay protection device includes a measurement part, a logic part, a fixed value adjustment part and an execution part. The measurement part refers to comparing the input signal from the protected object with the given setting value to judge whether there is a fault or abnormal operation state. According to the size, nature, order of appearance or combination of the output of the measuring part, make a logical judgment to make the protection device work according to a certain logical relationship to determine whether the protection should act. The execution part executes the circuit breaker trip or sends out an alarm signal according to the result judged by the previous link.
——————————————
1. AC and DC (manual automatic test)
output voltage/current signal
2. Low-cycle load shedding protection
Low-cycle load shedding is generally used in large enterprises with self-provided power plants . When the frequency of the power supply drops to a certain value, equipment or other accidents will occur, such as bearing bush burning, reduction of machining accuracy, etc. Therefore, low-frequency load shedding protection is set up on the power grid. When the grid frequency is lower than the set value, the protection will cut off the loads one by one according to the pre-input load shedding list until the grid frequency returns to the allowable value range. (belongs to line protection)
The low cycle load shedding module includes frequency action value, action time, slip (df/dt) blocking value test, low voltage blocking value test, low current blocking value test and other items.
Frequency conversion point by point, accurately simulate the process of system frequency decline. When the frequency changes in each step, the output remains for a period of time (i.e. hold time) to ensure that the protection action reversal signal can be received. In this way, the low-cycle protection action value can be accurately measured, and at the same time, the protection of low-frequency blocking caused by the low frequency drop is avoided.
3. Low-voltage load shedding protection
4. State sequence
1. Output a series of states (voltage/current, output value, trigger condition) to measure trip time or other time.
2. The four digital output positions and holding time of each state can be defined separately for starting external devices.
State reversal conditions: time trigger, binary input trigger, button trigger, GPS trigger
5. Power direction
Transformer power direction protection (including phase-to-phase power direction protection and zero-sequence power direction protection), use the product of voltage and current to determine the current flow (phase ) relay protection. The current and voltage signals are obtained from the current transformer and the voltage transformer to determine the forward or reverse direction of the short-circuit fault at the protection device.
6. The whole group of transmissions (simulated faults) The whole group of transmissions completes the switch transmission test of overcurrent, high frequency, distance, zero sequence and other line protection devices and reclosing
by setting various test parameters and simulating various faults .
The test items that can be completed include: whole group transmission test of distance, zero sequence, overcurrent protection, etc.; reclosing action characteristics; GPS reversal of double-ended line protection.
—— —— —— —— —— ——
The "Entire Set of Tests" module provides a wide variety of failure modes. You can set a large current to make overcurrent protection, zero sequence protection, differential protection, and high frequency protection act; you can also set a small impedance to make distance protection act; you can also set these faults as transient faults, permanent faults or Conversion failure. In short, what kind of fault is set is not important, what is important is to trip the circuit breaker.
在其他多个测试模块中可以做重合闸试验，但“整组试验”对重合闸试验的检测更全面一些，设置方法也更简单。当我们需要做重合闸试验时可优先选用“整组试验”测试模块。
它的一般设置方法是：首先根据需要设置一个故障，过流、零序的话就把这个电流设置得大一些；阻抗保护的话就把阻抗设置得小一些。
所谓重合闸检同期就是在断路器重合闸时检测投入侧与被投入侧的电压相位。只有两侧电压相位差在允许范围之内时才允许重合闸，否则闭锁重合闸。
（1）按被保护的对象分类：输电线路保护、发电机保护、变压器保护、电动机保护、母线保护等；
（2）按保护原理分类：电流保护、电压保护、距离保护、差动保护、方向保护、零序保护等；
（3）按保护所反应故障类型分类：相间短路保护、接地故障保护、匝间短路保护、断线保护、失步保护、失磁保护及过励磁保护等；
七、差动保护
变压器差动保护中最重要的是差动电流以及制动电流的计算，而这两项电流的计算与平衡系数和转角公式有关。
平衡系数是为了消除变压器各侧电流因为TA变比不一致带来的不平衡电流；转角公式则是为了消除因为变压器各侧绕组的接线型式不一样而带来的不平衡电流。
Y/Δ-11接线：高压侧线电压超前低压侧线电压30度。
差动电流：Id=| Ih + Il|
制动电流：Ir
平衡系数：（高压侧、低压侧）
测试项目：比率差动、谐波制动、间断角制动
标幺值＝有名值(实际值)/基准值。例如实际值为 38.5kV 的电压，当选取35kV为
基准值时，其标幺值为1.1，当选取110kV为基准值时，其标幺值为0.35。
保护对象：差动电流门槛值Icd、差动电流速断值Isd、整定动作时间、基波比例制动系数、谐波制动系数：
某保护的定值为：变压器容量：6300 KVA；高压侧额定电压35 KV；高压侧 CT变比 150 / 5；低压侧额定电压 6 KV；低压侧CT变比 400 / 5；门槛值：2 A；速断值：10A；拐点值：4 A；比例制动斜率：0.5 ；低压侧平衡系数：1.38；变压器接线类型：Y / ∆-11，谐波制动系数：0.18。计算高、低压侧额定电流
Ie1 =(6300 /35) / (150 / 5) = 6 A； Ie2 =(6300 /6) / (400 / 5 ) = 7.88 A
差动门槛、差动速断值检验：一般实测的动作电流是保护门槛定值的1.732倍，这是因为保护在处理星-三角转换时，已考虑了数值和相位的补偿问题，否则实测的动作电流应等于保护的门槛定值。
测速断前，先通过保护的控制字将“比例制动”保护退出，试验的方法同上。一般实测的动作电流是保护速断定值的1.732倍。如果1.732倍的速断动作值很大，可以采用测试仪两相电流并联输出（两相电流相位应相同），也可以将保护中的速断定值设置得小一些。
比率制动系数测试
设置IA = Ie1 = 6 A,相位为0º；IB = Ie2 = 7.88 A，相位为180º；IC = Ie2 = 7.88 A，相位为0º；并且设 IA 为变量，步长为0.1A。点击“开始试验”按钮，保护应不动作。逐步减小IA至保护动作，记下此时IA、IB的值，假设IA=5.5 A，IB=7.88 A。这样，第一组数据测试完毕，还可设初始的IA、IB（IC）分别为1.5倍、2倍、2.5倍及3倍的高低压侧的额定电流。当然,也可以随机取一组IA、IB值，只要保证开始试验保护不动作。并且，也不必局限于减小变量至保护动作，增加变量也能使保护动作，测得的数据同样满足要求。依据上述方法，测试出其它几组保护动作时的IA、IB的值，以便多验证几组数据。
八、距离保护与零序保护
接地距离保护是利用短路电压和电流的比值，即测量阻抗的变化来区分系统的故障与正常运行状态。而零序保护利用的是接地故障时产生的零序电流分量。
接地距离保护的灵敏性高于零序电流保护（距离保护利用了短路时的两个电气量，自然比单一的电流保护要灵敏）。在线路发生故障时，首先距离保护动作，零序保护作为后备可能动作。
距离保护和电流保护一样是反应输电线路一侧电气量变化的保护。接地距离保护一般用在220kV及以上电网中，当零序电流Ⅰ、Ⅱ段不能满足要求时使用。
三相电流平衡时，没有零序电流，不平衡时产生零序电流，零序保护就是用零序互感器采集零序电流，当零序电流超过一定值（综合保护中设定），综和保护接触器吸合，断开电路。
九、线路保护
线路保护模块提供了零序电流定值、负序电流定值、阻抗定值的校验以及z/t动作阶梯、自动重合闸及后加速、非全相零序保护定值校验、工频变化量阻抗元件定值校验、最大灵敏角测试等测试项目。
十、重合闸后加速
重合闸后加速：当被保护线路发生故障时，保护装置有选择地将故障线路切除，与此同时重合闸动作，重合一次。若重合于永久性故障时，保护装置立即以不带时限、无选择地动作再次断开断路器。
重合闸和备自投是电网中快速恢复供电的两种最重要最常见的自动装置。不同之处在于：重合闸投入的仍是原线路本身，备自投投入的是另一路电源。
检同期和检无压：在重合闸（或备自投）中实现的一种方式和手段。也就是说，重合闸和备自投都分为检同期和无压两种方式。
检同期是指在合开关前，对断路器两端的电压进行同期判定。如果电压幅值差和相角差在允许范围内，则断路器允许合闸，否则合不上。
检无压是指在合开关前，先检测开关线路侧是否有电压，确定无电压后，再合开关。
测试重合闸检同期、检无压及重合闸后加速。可模拟重合前、后两次故障。两次故障的短路阻抗和短路电流的大小可以分别设置。
重合闸及后加速模块包含：
故障前状态：显示故障前电压、电流的幅值和相位以及相应的矢量图。
故障状态：显示故障状态下电压、电流的幅值和相位以及相应的矢量图。
跳闸后状态：显示跳闸后电压、电流的幅值和相位以及相应的矢量图。
要模拟重合闸及后加速动作情况，应在“故障方式”选项中选择“永久性故障”。
十一、自动准同期
同期继电器或自动准同期装置用于：发电机的并网；电网中两个部分的连接；断路器手动合闸；同期检测。
同期装置通过测量两个电压的相角、频率和幅值，防止两个不同步系统并网操作。当发电机连接到网络时，同期继电器必须控制发电机的启动并在正确的时间及时将其并网。
当使用自动准同期时，准同期装置会自动调节待并网发电机的电压、频率和相位与电网相同，当调整到具备并网条件时，自动合上发电机的同期合闸开关，完成发电机的自动并网。
十二、反时限过流保护
反时限保护多用于电动机保护。当被保护设备（如电动机）出现故障时，故障电流（或称短路电流）越大，该继电保护的动作延时越小，即：电流和与动作时间成反比。
输入电流到过流保护继电器，测试其动作时间。通过多个点的测试得到保护实际的电流时间动作特性。