This Standard was published on 19 May To maintain their currency, all Standards are periodically reviewed, and new editions are published. Between editions, amendments may be issued. Standards may also be withdrawn.
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It addresses fire risk issues and improves design and installation practices. What are Isolators? They have the capacity of making, breaking and carrying currents in normal circuit conditions and in specific overload conditions. Circuit breakers have the additional ability to automatically interrupt overload currents, while switch-disconnectors do not.
Amendment 2 contains significant changes for sizing and installing switch-disconnectors, but not for circuit breakers. Figure 1: Isolator schematic Main Changes in Amendment 2 Amendment 2 introduced new installation and product requirements for switch-disconnectors to improve the uniformity of product datasheets and ensure the isolators can withstand the harsh Australian climate.
The main changes are: Switch-disconnectors must now be compliant to AS Isolators must be sized to the rating corresponding to the utilization category DC-PV2. Standardising and simplifying the temperature effects and corresponding isolator rating. The manufacturer must provide corresponding current ratings for each scenario. Introduction of a new method to size the isolator. Additional exception for inverter-integrated isolators: Isolators integrated to the enclosure of the isolator can be used if requirements outlined in Clause 4.
The inverter manufacturer can provide advice concerning this. PV array open circuit voltage corrected for lowest expected temperature i. PV Array Maximum Voltage. PV array short circuit current multiplied by 1. Installation location of the isolator indoors, outdoors, or outdoors but fully shaded.
Apply the three steps below. The isolator must meet all requirements to be used with the chosen array configuration. The sizing process can be different for inverter-integrated isolators, so refer to the inverter manufacturer or their installation manual if intending to use the in-built isolator.
Step 1 — Thermal effects Check that 1. This ensures the isolator can interrupt maximum current even during high temperatures. Step 2 — Operational conditions. Consider the isolator configuration when the positive and negative conductors are operating in series Figure 2.
This ensures the isolator can interrupt maximum current under normal operating conditions. Figure 2: Isolator operation under normal conditions: Ie Step 3 — Fault conditions For non-separated transformerless inverters only.
Consider the isolator configuration when the positive and negative conductors are not operating in series Figure 3.
This ensures the isolator can interrupt maximum current under earth fault conditions. However, doing this may degrade the isolator, so it should be replaced after it is used to isolate the system under fault conditions. The system has a PV array maximum voltage of V and an array short circuit current of 17 A.
The following example checks whether the isolator selected is suitable for this purpose. Table 1: Isolator datasheet.
A Guide to AS/NZS 5033:2014 Amendment 2 Changes to Isolator Sizing
Download: As/nzs 5033 Free Download.pdf