Trade analytics for risk mitigation

List of the catalog of this article:

• 1,Trade analytics for risk mitigation What is a small grounding current system
• 2. What is a small grounding system?
• 3, When a single-phase grounding fault occurs in the system, the capacitance and line voltage of the small grounding and large grounding current systems to the ground...

What is a small grounding current system

The neutral point is not grounded or through the arc Circle grounding system, occur singleWhen the grounding fails, because it does not constitute a short-circuit loop, the grounding short-circuit current is much smaller than the load current. This system is called a small-current grounding system.

Single-phase grounding of the power system refers to the grounding of one of the three phase lines of the power line, which is a fault phenomenon. The small grounding current system is a wiring mode and operation mode of the power system. It generally refers to the neutral point non-grounding system and the neutral point through-arc coil grounding system.

The so-called power supply "small grounding current system" is actually a branch of the power supply neutral point ungrounded system. It is grounded through a high resistance (or equivalent high resistance) at the neutral point of the power supply.

What is a small grounding system?

1. High-current grounding and small-current grounding are grounded by neutral points in the power system, which are distinguished according to the main operating characteristics. The small grounding current system is also known as the ineffective grounding system. Including neutral point non-grounding, extinguishing arc coil grounding, and high-impedance grounding system.

2. When a single-phase grounding fault occurs in a neutral point direct grounding system (including a system grounded by a small impedance), the grounding short-circuit current is very large, so this system is called a high-current grounding system.It adopts a system that is not grounded at the neutral point or grounded by an arc coil.

3. The so-called power supply "small grounding current system" is actually a branch of the power supply neutral point ungrounded system. It is grounded through a high resistance (or equivalent high resistance) at the neutral point of the power supply.

4. For 10kV systems, there are common ungrounded systems, mainly because the capacitor current is relatively small, and the damage to the equipment is relatively small when single-phase grounding occurs. It can operate with faults and provide maintenance time for maintenance personnel. The speed of finding faults can be improved by equipping a small-current wire selector.

When a single-phase grounding fault occurs in the system, the capacitance and line voltage of the small grounding and large grounding current systems to the ground...

The characteristic of a small grounding current is that when a phase grounding fault occurs, the grounding current is limited to a smaller value, and the ground steady-state voltage of the non-fault phase may reach the line voltage. The large grounding current system is also known as the effective grounding system. Including neutral point direct grounding and low-impedance grounding systems.

In the non-grounded system of the neutral point, when the insulation of any phase is destroyed and grounded, the line voltage between the phases remains unchanged, and it can continue to operate with faults, and the ground voltage and the ground capacitance current of each item change, and the point of the neutral point is far from the earth potential.

The neutral point is not grounded, and the earth and the system are not electrically connected.

When one-phase grounding occurs in a small-current grounding system, the grounding relative voltage is zero, and the other two relative ground voltages increase by three times.The magnitude of the grounding current at the contact point is equal to the sum of the grounding capacitance current of all lines.

When a single-phase metallic grounding occurs in a small current grounding system, the ground relative voltage is zero, and the non-ground relative ground voltage rises to line voltage.

Small grounding current grounding (i.e. ineffective grounding) includes: neutral point non-grounding, high resistance grounding, extinguishing arc coil grounding method, etc. When a single-phase grounding fault occurs in a small-current grounding system, because the neutral point is not effectively grounded, the fault point will not produce a large short-circuit current, so the system is allowed to operate with faults for a short time.