Electrical safety: When good grounds go bad
With electrical equipment, there's often high confidence in good, solid, earth grounding for protection. In some situations unexpected "ground voltages" can cause serious instrumentation errors, not to mention safety concerns, warns Dataforth . Fortunately, there are ways to protect personnel and control components from unexpected ground or neutral-wire voltages.
Protection for power-hungry equipment includes circuit breakers with ground-fault detection built-in, surge protectors, lightning arrestors, uninterruptible power supplies with voltage regulation built-in, and other like devices.
Recommended protection for instrumentation includes isolating channels from one another and from ground. Isolating test and measurement systems and process control systems assures long, trouble-free, worry-free performance, Dataforth says.
The company's isolated signal conditioners, for instance, provide three-way isolation. The signal path, the electronics on the sensor side, and the electronics on the system side are all isolated from ground. Isolated signal conditioners provide excitation voltage and isolated excitation voltage for 4-20 mA loops, strain-gages, and LVDTs.
A Dataforth white paper covers common topologies used in industry to connect single-phase and three-phase systems, show how voltage distribution panels distribute working voltages and neutral and ground wire connections. Click here for the full Dataforth application note, "When Good Grounds Go Bad," available in PDF.
—Edited by Mark T. Hoske , Control Engineering editor in chief