The fault then escalated in to a phase-phase A-B fault. The waveform capture shows a phase-ground or line to ground fault which then evolved in to a phase-phase fault. Phase-Ground fault starts at dotted red cursor and ends at magenta cursor. Phase-Phase fault starts at magenta cursor. Top graph shows line voltage. Middle graph shows phase current and bottom graph shows ground current. Negative sequence current exists during a phase-ground fault and during phase-phase fault.
Zero sequence current exists during a phase-ground fault only and does not exist for phase-phase fault. All sequence currents during L-G fault. During phase-ground fault positive, negative and zero sequence currents become approximately equal as can be observed on the above graph. The reason for this can be seen if the sequence impedance circuit provided below is studied.
During the phase-phase fault, positive I1 and negative I2 sequence current becomes equal while zero sequence I0 current disappears. Forums New posts Search forums. What's new New posts. Log in Register. Search titles only. Search Advanced search…. New posts. Search forums. Log in. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly. You should upgrade or use an alternative browser. Thread starter Pcore Start date Jun 10, Pcore New member. Location Leroy, NY. When measuring phase to ground on each phase of the secondary side we have one phase that measures zero, the other two measure V.
Phase to phase they all measure V. I'm inquiring if anyone knows if this could be a safety concern or why this might of have been done this way?
Location Connecticut Occupation Engineer. You have a corner grounded delta. I can't think of any particular safety concerns with that system, but maybe someone else will have more insight.
As David mentions, you may have a 'corner grounded delta', where one of the three phases is intentionally connected to ground to provide a solid ground reference. This is done for much the same reasons that a neutral if available gets grounded. Ungrounded delta systems are used to permit systems to continue operating in the event of a single ground fault. However when this fault occurs, it is important to locate and repair it.
Location Portland, ME. The only suggestions I have: Be sure it's deliberately corner grounded and not an ungrounded system with a single phase fault. If it is a deliberate corner ground, be sure it was installed properly: Real common to open feeder disconnects and find fuses in the grounded phase. JeffBabineaux Member. With an ungrounded system, one ground fault can be un-detected, That means that the voltages with respect to ground and the consequences of a ground fault are not predictable.
With one phase grounded, the effect of a ground fault is not the same everywhere in the system. If the neutral is grounded, the voltages with respect to ground is limited to the line-to-neutral voltage. Therefore a star system with a grounded neutral is preferred. Sign up to join this community. The best answers are voted up and rise to the top.
Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Grounding of one pahse of a starpoint where the point is not grounded Ask Question. Asked 4 years, 8 months ago. Active 4 years, 8 months ago. Viewed 1k times. With single phase loads connected to each live. All loads and components are balanced. Update: simulate this circuit — Schematic created using CircuitLab To clarify the question: I see two possible outcomes: as in Charles Cowie answer, the circuit operates as normal as there is no other ground path.
I hope this clears up the question. Marked Marked 1 2 2 bronze badges. If you do that in a V system, then you basically talk about the phase to phase voltage, hence people call those systems often V systems.
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