Nps Overvoltage Elements; Nvd Overvoltage Elements; Frequency Elements; Figure 2 - Nps Overvoltage Element - Siemens Argus 8 7SG11 Manual

3.3

NPS Overvoltage Elements

Some Argus 8 variants have, depending upon their configuration, 2 NPS overvoltage elements. If the NPS (V2)
input exceeds the setting value the starter will pickup unless any of the inhibits are enabled. Figure 2 shows the
basic operation of each NPS overvoltage element. The 'event' and 'instrument' labels in the diagram indicate
where this type of information is generated.
NPS (V2) Pickup Value
(VA & VB & VC)
☯
V Block Threshold
(V2 Element Inhibit)
Status Input
3.4

NVD Overvoltage Elements

Some Argus 8 variants have, depending upon configuration, 2 neutral voltage displacement (NVD) overvoltage
elements. The neutral or residual voltage can be measured directly from an open delta tertiary winding or
calculated internally from the three phase voltage inputs.
If the relay is configured so that the residual voltage is measured directly, then this value is fed to the element
starter directly. Also, a 3Vo V.T. ratio setting will be made available. If however, the residual is calculated from the
3 phase input voltages, then 3 x Vo is fed to the element starter. (Vo is the zero sequence voltage ).
If the NVD input exceeds the setting value the starter will pickup unless an inhibit is enabled. Figure 3 shows the
basic operation of each NVD overvoltage element. The 'event' and 'instrument' labels in the diagram indicate
where this type of information is generated.
3 x ZPS (3Vo) Pickup Value
Status Input
3.5

Frequency Elements

Argus 8 - 200 series variants have 4 frequency elements as standard. These can be configured as either
underfrequency (U/F) or overfrequency (O/F). Each element can be inhibited in four different ways :-
1. If all phase voltages fall below the voltage blocking threshold level.
2. Via a status input inhibit signal.
3. Via any combination of voltage elements starting.
©2010 Siemens Protection Devices Limited
Event
Block
1
Event
Instrument
(3Vo Element Inhibit) Block
Event
Instrument
7SG11 Argus 8 Description of Operation
NPS DTL
& Element
Starter
Event
Instrument

Figure 2 - NPS Overvoltage Element

NVD DTL
& Element
Starter
Event
Instrument

Figure 3 - NVD Overvoltage Element

Trip
Event
Instrument
Trip
Event
Instrument
Chapter 1 Page 9 of 20