Siemens UL1066 Voltage Transformers, VT Accuracy, Maximum distance from voltage transformer

Communication-capable Circuit Breakers

WL Circuit Breaker

The trigger event can be set individually for each waveform buffer. The point at which the trigger event is to take place in the waveform buffer can also be defined. This setting can be used to set the ratio of the pre-event history to the post-event history. If the pre-trigger event history is to be analyzed, the position can be set to 80%. When the event occurs, 0.8 seconds of pre- event history and 0.2 seconds of post-event history are available in the waveform buffer, and an existing COM16 module adds a time stamp to the trigger event.

Each waveform buffer stops independently, depending on the trigger event and can be activated again once the analysis is complete.

A large amount of data (approx. 25 kByte for each waveform) can be downloaded and analyzed using WinPM.Net, the BDA and the ETU776 display. Depending on the option,

a range of zoom options and export functions are available.

Voltage Transformers

For isolation reasons, a voltage transformer is used in conjunction with the Metering Function Plus module. This prevents voltage signals of up to 1kV from reaching the ETU directly via the auxiliary secondary connections.

The metering module (“Metering Function Plus”) can be set to expect 3W or 4W (LL/LG) connections and will adjust the amplitude and phase of the signal as necessary.

Three VTs must be used at all times.

All three VTs should be rated for the nominal system L-L voltage (e.g. 480V) and may have either 100V, 110V or 120V secondary voltages.

The following ratios and suggested and equivalent VTs can be used: 240:120 = 2:1

(ITI Part # 460-240 or 468-240) 480:120 = 4:1

(ITI Part # 460-480 or 468-480)

2/15

600:120 = 5:1

(ITI Part # 460-600 or 468-600)

VT Accuracy

Each Metering Module presents a purely resistive (unity power factor) load to the transformer. Assuming no other devices connected to the VT, a ITI type 486 VT can safely feed 10 metering modules and and still maintain 0.6% accuracy assuming the wiring from the VT to the individual metering modules is twisted pair and kept to a minimum length.

This data applies to ambient temperatures from 30ºC to 50ºC and a primary voltage from 80% to 120% Vn.

Maximum distance from voltage transformer

The maximum distance between the metering function and the voltage transformer depends on the cable size and the desired accuracy class.

Metering VT Settings:

Delta/Wye : Delta

VT Primary: 480 (for example)

VT Secondary: 120 (for example)

Metering VT Settings:

Delta/Wye : Delta

VT Primary: 480 (for example)

VT Secondary: 120 (for example)

For a 14AWG cable, the maximum distance should not exceed 50 m for class 0.5 and 100 m for class 3. In areas with high EMC exposure, shielded cable should be used.

Parameters for the settings of the metering function

The trip unit settings which must be made are:

1)VT Primary Voltage (240V, 480V, 600V)

2)VT Secondary Voltage (100V, 110V, 120V)

3)VT Connection (Wye / LG, Delta / LL)

The following tools and functions are available if the parameters have to be changed:

•WinPM.Net

•WL Config

•BDA/BDA Plus

•ETU776 display

Note: Required primary and secondary overcurrent protection (fusing) not shown for clarity.

WL MODBUS Communication and Electronic Accessories • January 2005