P343 Hi Z Diff CT Ratio

[JulianPickett]

Hi, I have a technical issue with a Micom P34331RDLM0B58M serial Number 37208986/09/25. If I set the differential protection to High Impedance mode and the settings are in primary values, changing CT1 ratio alters the high impedance diff setting? (Changing CT2 ratio has no effect on the Diff setting). The manual states that high impedance diff. CTs should be connected to IA-2, IB-2, IC-2, which they are and I can confirm that secondary injecting these CT inputs displays the correct ratio and values on IA-2, IB-2, IC-2 display in measurements, and the relay trips on Diff when these CT inputs are injected. Why is it that changing CT1 ratio affects the setting of High Impedance Diff when they are clearly associated with CT2 inputs?

Kind regards,

Julian Pickett

[Manon_Chaboud]

Hello @JulianPickett, thank you for your post, we'll come back to you!