The Featured Image shows 15,000 Volt Breaker Cells, Protective Relays that Measure Various Parameters of Operating Equipment, and a Magna-Blast 5,000 Volt Breaker that is lifted into place by an Elevator Mechanism. The Black Rectangles at the Top of Each Cell Door for the Left and Middle Photos are Protective Relays, Discussed below.
Meters and Measuring Devices are indispensable items. Measuring minute resistance, to tremendous amounts of current, things must be known about machines and processes around us. At work, my supervisor that came later in my career there, thought an electrical problem in the shop should be resolved by pulling in new wire, and using a larger amperage circuit breaker.
The problem was a breaker tripping. Over the years, circuits were added willy nilly, I’m afraid Code for electrical wiring wasn’t always adhered to, and yes, it was possible that too much was on the Circuit Breaker, but that wasn’t likely to suddenly arise. It was hot, the Window AC was running, and once in awhile, the breaker would trip.
Supervisor suggests larger gauge wiring and bigger breaker. The electrician leader; one of the union guys given additional responsibility, it was his office AC; takes a clamp-on ammeter, isolates a single wire at the AC Receptacle to measure, turns on the AC, and voila, the AC is pulling 15 amps, it’s rated for well under 10 amps. He makes a call to the refrigeration dept, in 20 minutes, they have a replacement AC, plug it in, draws well under 10 amps, and the breaker stopped tripping. Much simpler than rewiring the shop, eh?
As I wrote this (it was supposed to “As I Write This” but I fell asleep), the room felt hot, I measured the temperature, it was 78. And it felt humid too. I measured that, it was 55% humidity, I got up (I was in bed, I’m usually up late) and set the AC thermostat cooler. That dropped the room temperature and humidity.
Science at it’s finest, no need to guess.
At work, we had massive amounts of electrical equipment. 13,800 Volt Motors, 4,160 Volt Motors, and lower voltage motors all over the place. But to be sure that motors did not fail dangerously, at least not often, there were relays that controlled Circuit Breakers, BIG Circuit Breakers. Instantaneous and Timed Over Current, Under Voltage, Phase Reversal (on the Bus Relays), Under-Power (this one was installed on some motors due to a coupler failure that left the motor running without its compressor attached, and being that a fire ensued, it would be better if the motor shut off, the Under-Power Relay opens the motor’s Breaker if the Motor suddenly sheds its load), Ground Fault, and probably a few that I’m missing.
But measuring is something we take for granted. These devices Measure the Current and current can increase due to problems with the process and the motors need protected from that or can increase due to problems with the motor, they Monitor for Grounded Circuits, and Monitor for Voltage. If something goes wrong, in so many cycles of power, they open the breaker, (depending on how they are designed) or Close a Breaker (Undervoltage Relay will Open a Bus Feed Breaker and Close a Bus Tie Breaker to keep a system powered that otherwise would have lost power). We had old style Electro-Mechanical Protective Relays, we were gradually getting Electronic Ones, but it’ll take time and acceptance. We know the old ones worked. They were regularly maintained and tested, as were the Circuit Breakers.
Here’s an Overview of Electro-Mechanical Relays, these are used to Open or Close Breakers similar to the one shown in the attached image, or larger or smaller breakers.
Electrical Power Training – Electro-Mechanical Relays
Protective relays — demo unit (relays installed in door)
ANSI Device 60 Voltage Unbalance Relay
Bottom Line, Measurements are going on all around you, your Smoke Detector is looking for particles to show on Photo-Electric Detectors, or react to the Ionization Detector, CO Detector is waiting for a threshold Voltage to develop, Sensors on the Car are looking for a variety of things, and so much more. It’s nice to be able to measure Humidity, Temperature, Barometric Pressure, etc. It’s essential to measure Resistance, Voltage, Current, and Power. These are things indispensable for modern life and few of us ever give it a thought.