Blog Reading
Home » Blog » Questions » Change phase sequence

Change phase sequence

It is absolutely impossible for a utility to change the phase sequence. Why? Because the utility is connected to the local grid, the local grid to the regional grid, the regional grid to the national grid, and the national grid to the international grid. So, unless you don't change the phase sequence in the entire network you cannot change it locally. What will happen if one will change the phase sequence and phase A will come in phase B's place? If everything is operational nothing will happen. And that's because the breaker will not close since it will be never possible to synchronize the two networks. If someone will be smart enough to close the breaker without synchronization, than the breaker will become a piece of junk and some other breakers will open on the network to isolate the fault here.

OK. Now suppose that our factory is the only one connected to a substation through a line. If some works are to be done in the substation on this cell, your factory probably has another energy supply and will energize the affected busbar through the meaning of the second power supply (spare). This is done by first connecting the second power supply to this busbar (with synchronization check) and then disconnect the main breaker of the line that needs work. When the work is done and you have to connect back the main line, the operations are the same, you close the main breaker with synchronization check and if somebody have mess the things up and changed 2 phases, the breaker will not close.

Now, the only way to change 2 phases:
The utility needs some work on the line thus de-energize the line. All equipment that are connected to that line is not energized from another source! This is sometime possible but first of all, the utility have to check the phase sequence after every work that can lead to a phase sequence change. And I can assure you that this check is done every time just because the effects of a such mistake can be disastrous. More than this, the client connected to the utility has to check by himself the phase sequence that is available in the incoming lines. Remember that all the power was out for this client so, when the power is back available, the busbar that will be energized from the incoming line will be free of any load (all the breakers on the busbar in open position, except the breaker for the measuring cell if applicable).

In power generation, distribution and transport, the rules are very clear and are obeyed by every professional. If the basic rules of the energize- deenergize operations are not followed, the company must fire the one in charge with the management of this department.
In addition, there are some automation and interlock systems that prevent the operators to do some mistakes.

You may also like:

I have been involved in the design for production of many power electronic products, including switching power supplies, electronic ballasts and automotive electronics for Hybrid vehicles. What I have found is ...
whatever AC drive you pick should be from a supplier who is as LOCAL as possible and can support you when things are not going as planned. Most use the same or similar technology (otherwise they would not ...
You can even get low cost variable frequency drives with low commutation resolution (8 bit and less) that WILL cause more audible noise in EITHER type motor irregardless of PWM frequency! The variables are ...
Frequency directly represents no of rotation of rotor for that machine, the higher the frequency the more the rotation of the rotor, i.e. the rpm of the motor there by result in bearing wear and tear, if ...
Driving the motor with sinusoidal voltages conveniently eliminates the issue of dv/dt related problems, voltage doubling effects and common mode currents flowing into the motor. The motor-side inverter of the ...
service The engineers in AC Drive China are very professional in Chinese automation industrial control fields, provide you comprehensive energy saving solutions.

Hot Tags

Featured

Frequency directly represents no of rotation of rotor for that machine, the higher the frequency the more the rotation of the rotor, i.e. the rpm of the motor there by result ... Due to power electronics technology and microelectronics technology rapid development, variable frequency drive reforms and upgrades speed also is faster, introduce new products, ... Since the 21st century, China variable frequency drive industry is highly fission. Many foreign brands begin to set up factories in China, the implementation of the localization ... My personal preference is for an AC line reactor simply because it does a better job of protecting the variable frequency drive from the line and the line from the drive. I've ... As nowadays there is a trend in green energy production and energy efficiency, what solutions/applications would you recommend in reduction consumed energy of a motor driven by ...

What's New