Voltage Protection: Phase Under/Over Voltage (27/59); Figure 3.10-1 Logic Diagram: Under/Over Voltage Elements (27/59) - Siemens 7SR224 Description & Operation

(1) Description of Operation 7SR224
3.10 V P
OLTAGE
In total five under/over voltage elements are provided. Four elements are provided for the 'Phase'
Voltages and one for the 'Auxiliary' input voltage.
The relay utilises fundamental frequency RMS voltage for this function. All under/over voltage
elements have a common setting to measure phase to phase (Ph-Ph) or phase to neutral (Ph-N)
voltage using the Voltage Input Mode setting.
Voltage elements can be blocked if all phase voltages fall below the 27/59 U/V Guard setting.
27/59-n (27/59-Vx) Setting sets the pick-up voltage level for the element.
The sense of the element (undervoltage or overvoltage) is set by the 27/59-n Operation (27/59-Vx
Operation) setting.
The 27/59-n O/P Phases setting determines whether the time delay is initiated for operation of any
phase or only when all phases have detected the appropriate voltage condition. An output is given
after elapse of the 27/59-n Delay (27/59-Vx Delay) setting.
The 27/59-n Hysteresis (27/59-Vx Hysteresis) setting allows the user to vary the pick-up/drop-off
ratio for the element.
Operation of the under/over voltage elements can be inhibited from:
Inhibit 27/59-n
27/59-n VTSInhibit: Yes
27/59-n U/V Guarded

Figure 3.10-1 Logic Diagram: Under/Over Voltage Elements (27/59)

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: P
ROTECTION HASE
A binary or virtual input.
Operation of the VT Supervision function.
Under voltage guard element.
U /O V
NDER VER OLTAGE
(27/59)
©2009 Siemens Protection Devices Limited