Hello—I’m a long time lurker and first time poster!
My question is about detailing the differences between an ungrounded system, a grounded system, and an insulated neutral system.
Here’s my understanding, and feel free to jump in where you deem appropriate:
An ungrounded system is found in many systems and was code until sometime in the 1950s. It is simple two wire. If an ungrounded system were to fail then it would create hot appliances that sent voltage to whatever they touched. Effectively the literal ground is the return path.
A grounded system is code for houses in the USA post 1950s. This system has several variants, but in general it has 3 wires. Hot, Neutral, and Ground. The ground is not considered a current conductor except for emergent situations. An emergent situation would be where the insulation breaks down, and the machine’s frame becomes hot.
The during an emergent situation the ground will create a low resistance (and higher amperage) path for voltage to ground and away from the environment. This improves safety by preventing fires, and electrocution. However because the grounding wire and the neutral wire is bonded behind the breaker, the system will shut down the piece of equipment.
A neutrally insulated system is one where the grounding is not bonded to the neutral behind the breaker. This system provides less safety than a typical grounded system, but it allows for the machinery to continue to operate. This system is favored on ships, and other systems where continued operation is a greater concern than human life. The major issue here is that if two phases go to ground then we get a high current short and breakers will open.
My question is about detailing the differences between an ungrounded system, a grounded system, and an insulated neutral system.
Here’s my understanding, and feel free to jump in where you deem appropriate:
An ungrounded system is found in many systems and was code until sometime in the 1950s. It is simple two wire. If an ungrounded system were to fail then it would create hot appliances that sent voltage to whatever they touched. Effectively the literal ground is the return path.
A grounded system is code for houses in the USA post 1950s. This system has several variants, but in general it has 3 wires. Hot, Neutral, and Ground. The ground is not considered a current conductor except for emergent situations. An emergent situation would be where the insulation breaks down, and the machine’s frame becomes hot.
The during an emergent situation the ground will create a low resistance (and higher amperage) path for voltage to ground and away from the environment. This improves safety by preventing fires, and electrocution. However because the grounding wire and the neutral wire is bonded behind the breaker, the system will shut down the piece of equipment.
A neutrally insulated system is one where the grounding is not bonded to the neutral behind the breaker. This system provides less safety than a typical grounded system, but it allows for the machinery to continue to operate. This system is favored on ships, and other systems where continued operation is a greater concern than human life. The major issue here is that if two phases go to ground then we get a high current short and breakers will open.
