7SG11 Argus 8 Description of Operation
1 Introduction
The Argus 8 series of Voltage and Frequency relays are numerical, multi-function devices, which have been
designed to be applied for the protection of generation, transmission, distribution and industrial systems.
•
Argus 8 - 100 series provide under / over voltage, negative sequence overvoltage and neutral voltage
displacement functions.
•
Argus 8 - 200 series provide under / over frequency functions in addition to the functions included in the
100 series.
•
Argus 8 - 300 series provide identical functionality to the 200 series but have a faster frequency element
operate time. Suitable for 50Hz systems only.
The protection functions available in the range have many possible applications, some of which are mentioned
below :
Under / overvoltage elements :
Four independent elements are supplied, each of which can be set to operate for under or overvoltage conditions
and all having separate DTL time delay elements. These can be used to protect generators against overvoltages,
motors against loss of supply or applied as backup protection in the event of defective system regulating
equipment.
Negative phase sequence (NPS) overvoltage elements :
Two independent elements are supplied, each of which has a DTL time delay element. These can be used to
monitor the quality of the supply and protect plant or feeders against system unbalance.
Neutral voltage displacement (NVD) elements :
Two independent elements are supplied, each of which has a DTL time delay element. These can be used to
detect earth faults in high impedance earthed or isolated systems. For this feature, the residual voltage can be
measured directly from an open delta tertiary winding or calculated internally from the three phase voltage inputs.
The NVD elements include a third harmonic filter, which de-sensitises the elements to any superimposed third
harmonic frequencies.
Under / overfrequency elements :
Four independent elements are supplied, each of which can be set to operate for under or over frequency and all
having separate DTL time delay elements. These can be applied wherever frequency protection is required to
maintain system stability e.g. in load shedding schemes. The accuracy and security of operation of the numeric
algorithms enables the relay to be employed to detect any frequency abnormalities.
Blocking operation :
Each protection element can be blocked from operation by a user defined status input signal. In addition, the
voltage, frequency, and NPS elements can be blocked by the Voltage Blocking Threshold, which has a variable
setting range. Also, each frequency element can be blocked by any combination of the voltage elements starting.
Argus 8 series of Voltage and Frequency relays are part of the comprehensive range of Argus-platform based
numeric relays. These relays have extensive control functions, which are supplemented by advanced metering,
data storage and fibre optic communications. Supervisory and self-monitoring features give added confidence to
the user as well as reduced maintenance and down time. A menu-based interface gives user-friendly access to
relay settings, meters and operational data.
The relay conforms to the relevant IEC 60255 standards.
©2010 Siemens Protection Devices Limited
Chapter 1 Page 4 of 20
