ABB Power/Ground Testing
Per ABB document, 3BUA000258-510 System 800xA Site Planning System Version 5.1:
“Verification and testing of the AC power distribution system and the grounding system is mandatory at the time of installation and before power is applied to the control system.
After that, the document tells you to contact ABB technical support.
I have an old copy of the testing procedure that was used by the Bailey Controls company. In its day, it was considered an industry standard. Does anyone know if ABB has similar test documentation?.
Please ask your regional ABB support center to assist you.
This topic has become "hot" during recent years when several large projects have run into problems due to, what has later been found improper grounding and installation.
I'm not aware of any test procedure, but the S800 I/O Getting Started (3BSE020923-510) document contain guidelines and requirements. The rules there were developed by our colleague Dr Sten Benda (now retired). For additional information, please read his book: http://www.amazon.com/Interference-free-Electronics-Applications-Sten-Benda/dp/
- Only one ground plane is discussed. If site has both "instrument" and "power" ground they must be well isolated from each other. There shall be no voltage difference between them. This is easily measured with a voltmeter.
- Where does the outgoing ground cable end up? Hidden under a rug in the next room, or properly grounded according to professional installation rules?
- Ground cable cross section area minimum is (35mm2 / 2 AVG). Braided ground straps have good characteristics and can be used, e.g. between cabinet and door. Ground currents can be measured with a clamp on ohmmeter.
- All ground connections should be properly made (paint must be removed, self tapping screws often provide better connection, professional clamping tools are preferred over DIY stuff, bolts and nuts should be of proper size and be tightened properly, etc.).
- DIN rails for use with S800 IO need proper support (e.g. mounted on a metal sheet) with self-tapping screws and no washers with a distance not exceeding 100 mm.
- All connections from ground up to the DIN rail should be of "low ohmic" type. The resistance between ground and any later point shall not exceeed 1 ohm. This is easily tested with an ohmmeter.
- Theoretically, there should be no currents in a ground cable. With poor installation (e.g. lack of grounding or grounding made with high resistance joints) ground current could travel in the instrument wires causing a wide range of problems.