Summation current transformers LU01

Technical specifications

Specifications are taken from the manufacturer’s technical documentation. Updated 11/13/2026.

Description

A summation transformer takes the secondary currents of several measuring current transformers working in the same phase and delivers a single current at its output. The typical case is several lines or feeders whose combined current has to be shown, recorded or sent to a meter. Without LU01 you would need a separate instrument on every line or have to add readings by hand. The output current is again a standard quantity, because the primary currents are added and then divided by the number of inputs, so the instrument scale stays familiar. The module is built in a plastic housing with terminals at the top and bottom and is mounted in a panel next to the measuring instruments. It matters that the summed currents are synchronous and share the same phase relation.

How to choose

The main criterion is the number of lines whose currents have to be added, since that is the number of inputs required. Also check that all main current transformers work in the same phase, because a sum of out-of-phase currents gives a wrong result. For a single feeder a summation transformer is unnecessary and an ordinary current transformer is enough. Before ordering, confirm the rated secondary current of the main transformers so that the summation inputs match them.