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Mutual monitoring of functional grounding and insulation resistance measurement sub-systems in a PV system

IP.com Disclosure Number: IPCOM000241998D
Publication Date: 2015-Jun-12
Document File: 2 page(s) / 47K

Publishing Venue

The IP.com Prior Art Database

Related People

Matti Jussila: INVENTOR [+4]

Abstract

This document discloses a design for a PV grounding and monitoring safety check. Both the PV functional grounding and the insulation resistance measurement are standard building blocks in a modern PV system. This disclosure demonstrates how these building blocks can be utilized in monitoring of the safe operation of both of them mutually.

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1.Abstract

This document discloses a design for a PV grounding and monitoring safety check. Both the PV functional grounding and the insulation resistance measurement are standard building blocks in a modern PV system. This disclosure demonstrates how these building blocks can be utilized in monitoring of the safe operation of both of them mutually.


2.Background

PV inverters have for years had insulation monitoring requirements coming eg from the safety standard IEC 62109. This means that most of the PV inverters have the option to measure insulation resistance of the PV generator prior to startup or during operation.

Also it is common for the PV generator to have functional grounding due to the PV module or standard requirement. In many cases the functional grounding is arranged within the PV inverter since the functional grounding and the insulation monitoring cannot usually be connected and operational at the same time and therefore the PV inverter must be able to control both of the functions.

In order to have safe and reliable PV system, the condition of the PV circuit and possible functional grounding should be checked intermittently. In order to be sure that the insulation monitoring is working as it should, it too should be tested.

Some of the insulation monitoring devices are known to have self-check functionality where the operation of the measurement circuit is verified utilizing internal circuitry. The verification or health check can be done by applying a known impedance between the circuit to be measured and the ground. If the insulation monitoring gives close enough values of the test impedance, then the measurement circuit is working as it should. In order to make sure that the measurement is not affected by other impedances than the test impedance, the measurement circuit is disconnected from the PV circuit for the test duration.


3.New solution

In the new solution the ability of the insulation monitoring and the functional grounding mutually monitor each other is being utilized. Figure 1 presents a PV inverter embedded health monitoring of the insulation monitoring and functional grounding sub-systems.

Functional grounding circuit usually has a predetermined size impedance which can be connected between one of the PV generator poles (DC pole of the PV inverter) and the ground. This impedance is measured with the insulation monitoring device a...