IDMT 选择性计算器
绘制反时限过电流继电器的动作曲线。
Reads IEC 60255-151:2009 / IEEE C37.112-2018. Tables checked 26 Sept 2026.
尝试一个工程 6
每项工作都会预填示例数值。请替换为您自己的数值。
- Grade two relaysThe operating times of a feeder and an incomer relay at 4 kA.
- Grade a very inverse pairThe operating times of two very inverse relays at 6 kA.
- Grade three relays in seriesThe margins between three relays at 5 kA.
- Find a relay's time at ten times pick-upThe operating time of one relay at 2 kA.
- Check an instantaneous settingWhether a 4 kA instantaneous element clears an 8 kA fault.
- Grade an extremely inverse feederAn extremely inverse relay under a standard inverse incomer.
输入
使用默认输入值的示例计算。
- 故障电流
- 1,200 A
- 继电器
- 2 行
Downstream 动作时间
0.27s
- Upstream 动作时间
- 0.96s
- 余量 Downstream 至 Upstream
- 0.68s
此结果仅供设计参考。请对照现行标准进行核验。
计算步骤
- 故障电流1,200A
- 继电器已分级2
- Downstream（IEC-SI）动作时间结果0.27s
IEC 60255-151:2009
- Upstream（IEC-SI）动作时间0.96s
IEC 60255-151:2009
- 级差裕度 Downstream 至 Upstream0.68s
关于此计算器
How this is calculated
The tool plots the trip curves of inverse-time overcurrent relays. It then checks the grading margin between relays at one fault current. Up to four relays are allowed, listed from downstream to upstream.
- Fault current. You enter the prospective fault current. The tool uses it for every relay.
- Multiple of pickup. For each relay, the tool divides the fault current by the pickup current. A relay does not trip at a multiple of 1 or less.
- Trip time. For an IEC curve, the tool uses the IEC 60255-151:2009 equation, with the time multiplier setting. For an IEEE curve, it uses the IEEE C37.112 equation, with the time dial. The curve constants come from the standard.
- Instantaneous element. If the fault current reaches the instantaneous setting, the relay trips at a fixed short time.
- Grading margin. The tool subtracts the trip time of each relay from that of the next one upstream.
| Step | Table or clause | What it decides |
|---|---|---|
| Curve shape | IEC 60255-151:2009 | The trip time of an IEC relay |
| Curve shape | IEEE C37.112 | The trip time of an IEEE relay |
| Margin | Your relay list | The gap between each pair of relays |
Worked example
- Two IEC standard inverse relays at 1200 A. The downstream relay has a pickup of 100 A and a multiplier of 0.1. The upstream relay has 200 A and 0.25. The downstream relay trips in 0.27 s. The upstream relay trips in 0.96 s. The margin is 0.68 s.
Limits
The tool uses the ideal curve equations. It does not model relay reset time, overshoot or current transformer saturation. It does not read curve data from a maker. An instantaneous setting of 0 means none.
The margin is for one fault current only. Check the margin at the highest and the lowest fault current at the relay. The tool does not choose settings for you.
See also: IDMT curve 100 A feeder grading, IDMT grading for a main switch and submain and IEC 60255-151 IDMT curve constants.
问题
结果仅供设计参考。请依据现行标准核对。
IDMT 计算器有什么作用？
工具可绘制最多四台反时限过电流继电器的动作曲线。它会报告在您输入的故障电流下每台继电器的动作时间。它还会报告列表中每两台继电器之间的选择性裕度。
有哪些曲线可用？
工具提供 IEC 60255-151:2009 的标准反时限、非常反时限、极端反时限和长延时反时限曲线。它还提供 IEEE C37.112 的中等反时限、非常反时限和极端反时限曲线。每条曲线都有各自的常数，因此相同的整定值会得出不同的动作时间。
哪些输入最重要？
曲线类型、启动电流和时间倍数决定曲线的形状和位置。故障电流决定动作时间的读取位置。瞬时整定为可选项。列表中的继电器顺序决定用于选择性配合比较的配对。
常见的注意事项有哪些？
继电器在动作电流以下不会动作，因此本工具在该范围内不报告动作。瞬时整定值在其阈值以上覆盖曲线。当选择性裕度低于 0.3 秒（本工具默认值）时会出现警告。继电器整定值保存在页面地址中。
计算示例
- Dairy shed IDMT relay setting and gradingThree IDMT relays at a 3000 A fault, two grading margins and one curve inversion between the shed main and the farm incomer, read off the AmpSize relay engine.
- IEC 60255-151: IDMT curve constantsWhat IEC 60255-151 governs, which curve sets the IDMT tool carries, and a worked grading pair on standard inverse that clears in 0.21 s and 0.74 s.
- IDMT curve grading for a 100 A feederTwo standard inverse relays at 2000 A give a feeder trip at 0.23 s, an incomer trip at 0.99 s and a grading margin of 0.76 s, read off one chart.
背景
本工具读取的条款和表格
- IEC 60255-151:2009 / IEEE C37.112-2018Inverse-time overcurrent curves
- IEC 60255-151 Table 1 / IEEE C37.112 Table 1IDMT overcurrent curve constants
表格最后核对于 26 Sept 2026。
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