Accusine PCS+ CT connection

[Mannguyen]

Hi all,

I'm trying to connect an Accusine PCS+ [model number] to a system where the Capacitor bank bus/Generator bus CT is applied together with the main bus CT, as shown in the attached diagram.

Do I need a summation CT at the interconnection point (marked in red) or can I connect directly to the Accusine's CT terminal port?

Could you please provide a connection diagram with your recommendations?

Thank you for your help.

[caimin_pan]

 You don't need a summation CT at the interconnection point. But the capacitor bank must be equipped with reactors to avoid amplifying harmonics and affecting the performance of PCS+.

[Mannguyen]

@caimin_pan The summation CT is not necessary is clear, but the reactors to be equipped with the capacitor bank to protect PCS+ cannot be included in the AHF offers, due to the complexity of sizing and calculating reactors based on the existing electrical system and impact on the price. Please advise the solution. Thanks again.

[caimin_pan]

The combination of capacitors and series reactors is necessary for power systems with harmonics, not just for protecting PCSP. The reactors （14% or 7%) are equipped with the capacitor bank , 14% reactor avoid amplifying harmonics of the 3th or higher order, 7% reactor avoid amplifying harmonics of the 5th or higher order. 

[Mannguyen]

Dear all,

Continuing with the CT connection method in combination with cases of the main bus CT and Cap. bank CT.

The image attached is a recommended diagram from FSSE for the CTs connection for PCS+, please help me with the parallel connection of the Main bus CT and Cap. bank CT whether it works or not? and advise if there is a proper way to combine these CTs into PCS+.

Thank you all in advance.

[Remi_Bolduc · Accepted solution]

Hi all, You will need summation CT's if you can operate in co-generation, however if you the gen set is a back up source of power, then you don't. However the current vector summation should be completed on an external terminal block, especially that you have a capacitor bank in the circuit. Keep in mind that CT polarity most be respected and all the CT's must have the same ratio. For optimized performance, it's always recommended to have CT's at the capacitor bank feeder even if the capacitor bank have tuning reactors.

[Mannguyen]

We installed some PCS+s to the customers with existing Cap. bank and we applied the CT summation for the combination of CTs into PCS+ with no issue, an SE field Services staff recently recommended that no need for the CT summation for the Main Incoming Bus CT and Cap. Bank CT connection as the attached diagram. However we are concerned about the paralleling connection of two separated CT sets, please advise if this type of CT connection has some drawbacks or disadvantages compared with the CT summation application.
Thank you in advance.

[Remi_Bolduc]

CT polarity on the primary side are fine. On the secondary for each CT on the same phase, make sure that all the X1 are together and all the X2 are together. Again, standard capacitor bank are not recommended in this type of application, the harmonic mitigation performance may be diminished.