Schwarzbeck CU 50561-1 Coupling Unit

The coupling unit CU 50561-1 belongs to the equipment for measurements at powerline transmission devices. The specifications for the measurements at PLC devices are included within the standard EN-50561-1.

Combined with two line impedance stabilization networks (LISN) the coupling unit provides a coupling system which guarantees defined conditions for the measurement.

To be able to measure the interference emission of a PLC modem especially at its maximum transmit level a transmission line with a defined RF attenuation has to be provided.

For this purpose two line impedance stabilization networks (LISN) as well as one coupling unit are required. The LISN provides mains to the EuT respectively the AE ports individually, see fig. 1 for an overview.

Fig. 1: Coupling System (EN 50561-1) 1

The coupling unit only bypasses the high frequency PLC signals with a defined attenuation. Combined with the LISNs the coupling system performs the following tasks:

• Providing a defined isolation between EuT and AE
• Stabilization of the impedance in common mode
• Attenuating the common mode signal from the AE
• Isolating the common mode signal to AE
• Separating the common mode and differential mode signals from mains

The coupling unit described in this document is built according to the standard. To verify the properties of the unit the attenuation characteristic has to be measured in a symmetrical 25 Ω system. The typical response characteristics is shown in fig. 2.

Each protective earth, phase and neutral is connected to each other in every connector box. The protective earth between the different connector boxes is not connected!

Handling:

The plugs have to be connected to the jacks of the LISN. The jacks in the housings of the coupling units are supposed to connect to EuT respectively AE.

Safety note: The measurement setup may only be set up while disconnected from mains! Hazardous voltages may occur at the connectors!

Further equipment is available for PLC measurements according to EN 50561- 1:

• SPLIT 100: resistive and symmetrical built splitter featuring three ports
• SYMAT 40: symmetrical, switchable attenuator with 0, 10, 20, 30, 40 or 50 dB attenuation and 100 Ω impedance.
• SY 9223-50561-1: 50 Ω unsymmetrical to 100 Ω symmetrical transforming balun and 8 dB attenuation
• ISN 50561-1: Impedance stabilization network for measurements of the asymmetrical interference voltage
• NSLK 8127: two path V-LISN

Fig. 2: Typical symmetrical transmission in a 25 Ω environment