Quick start manual

STER PMU Quick Start Manual Working with the instrument
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Using the up ( ) and down ( ) keys select the Current range menu item, and then use left ( ) and right (
) keys to select one of the two ranges:
 5 A (100% input range) or
 0,5 A (10 % input range)
Installed current transformers on the field are usually over-dimensioned for a possibility to add new loads in
future. In that case current in primary transformer can be less than 10% of rated transformer current. Moreover,
xxxA/1A current transformers are more common at HV systems then xxxA/5A usually used in LV levels. For such
cases it is recommended to select the 10% current range, which will allow increased precision.
To configure current transformer primary/secondary ranges press . When the CT submenu appears, use the up
( ) and down ( ) keys to select the Primary/Secondary current transformer range and press key.
Figure 4.7: Current transformer ranges setup
Primary current range can be set from 999 kA to 5A or lower depending on the Secondary range setting which can
be set in the range of 1A to 5A. By pressing the / soft function keys, user can alternate A/kA Primary
current range.
4.4 GENERAL CONSIDERATIONS FOR WIRING
Although the STER PMU can be accessed remotely to change configuration settings, it is nevertheless important to
configure the wiring properly if the device is intended to run during longer periods of time, at a distant location.
 Make sure that phases are correctly connected. To avoid confusion, current connector I1 and voltage
connector L1 should be connected to the same phase.
 Check the direction of the current flow. Current transformers should be mounted to measure the positive
direction of the current flow, from supply to load.
 Under the influence of parasite impedances, voltage terminals which are not connected (floating inputs) can
falsely measure unrealistically high values, creating large reading errors. It is therefore recommended to
connect (short-circuit) all unused terminals to the neutral connector.
4.4.1 CONNECTING VOLTAGE TERMINALS
IN I3 C B A I1
L1
L3C
N
A
I2
L2 B
GND
Neutral
Phase
First, connect the neutral voltage terminal (N) using the black
measurement cable, followed by three phase voltage
terminals (L1, L2, L3) using red measurement cables.
Green (GND) terminal can be used for measuring earthing
potential by using the green voltage measurement cable.
Always connect the cables to the device before
connecting them to live voltage.
Figure 4.8: Voltage terminals