低压配电系统是现代工业生产和日常生活中必不可少的电力设施，其安全性对人们的生命财产安全至关重要。为了保障低压配电系统的安全性，需要采取一系列的保护措施，如过载保护、短路保护、接地保护等。而这些保护措施的有效性需要通过测试、测量或监测来验证。

IEC 61557-3:2007 标准规定了用于测试、测量或监测保护措施的设备的回路阻抗的测量方法和要求。回路阻抗是指电路中电流通过时所遇到的阻力，它是保护措施有效性的重要指标之一。该标准规定了回路阻抗测量设备的技术要求，包括测量范围、测量精度、测量速度等。同时，该标准还规定了测量结果的处理和报告要求，以确保测试结果的准确性和可靠性。

IEC 61557-3:2007 标准适用于低压配电系统中的各种保护措施的测试、测量或监测，包括过载保护、短路保护、接地保护等。该标准的实施可以有效地保障低压配电系统的安全性，防止电气事故的发生。

相关标准
- IEC 61557-1:2007 Electrical safety in low voltage distribution systems up to 1 000 V a.c. and 1 500 V d.c. - Equipment for testing, measuring or monitoring of protective measures - Part 1: General requirements
- IEC 61557-2:2007 Electrical safety in low voltage distribution systems up to 1 000 V a.c. and 1 500 V d.c. - Equipment for testing, measuring or monitoring of protective measures - Part 2: Insulation resistance
- IEC 61557-4:2007 Electrical safety in low voltage distribution systems up to 1 000 V a.c. and 1 500 V d.c. - Equipment for testing, measuring or monitoring of protective measures - Part 4: Resistance of earth connection and equipotential bonding
- IEC 61557-5:2007 Electrical safety in low voltage distribution systems up to 1 000 V a.c. and 1 500 V d.c. - Equipment for testing, measuring or monitoring of protective measures - Part 5: Resistance to earth
- IEC 60364-4-41:2010 Low-voltage electrical installations - Part 4-41: Protection for safety - Protection against electric shock