the magnitude of polarizing voltage must be bigger than a minimum level defined
by setting UpolMin.
Note that –U2 is used to determine the location of the fault. This ensures the
required inversion of the polarizing voltage within the function.
7.5.7.3 External polarizing for negative sequence function
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The individual steps within the protection can be set as non-directional. When this
setting is selected it is then possible via function binary input BLKSTx (where x
indicates the relevant step within the protection) to provide external directional
control (that is, torque control) by for example using one of the following functions
if available in the IED:
• Distance protection directional function
• Negative sequence polarized general current and voltage multi purpose
protection function
7.5.7.4 Internal negative sequence protection structure
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The protection is internally divided into the following parts:
• Four negative sequence overcurrent steps
• Directional supervision element for negative sequence overcurrent steps with
integrated directional comparison step for communication based negative
sequence protection schemes (permissive or blocking)
Each part is described separately in the following sections.
7.5.7.5 Four negative sequence overcurrent stages
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Each overcurrent stage uses Operating Quantity I2 (negative sequence current) as
measuring quantity. Every of the four overcurrent stage has the following built-in
facilities:
• Operating mode (Off/ Non-directional /Forward / Reverse). By this parameter
setting the operating mode of the stage is selected. Note that the directional
decision (Forward/Reverse) is not made within the overcurrent stage itself.
The direction of the fault is determined in common “Directional Supervision
Element” described in the next paragraph.
• Negative sequence current pickup value.
• Type of operating characteristic (Inverse or Definite Time). By this parameter
setting it is possible to select Inverse or definite time delay for negative
sequence overcurrent function. Most of the standard IEC and ANSI inverse
characteristics are available. For the complete list of available inverse curves,
refer to Chapter
"Inverse characteristics"
• Type of reset characteristic (Instantaneous / IEC Reset /ANSI reset).By this
parameter setting it is possible to select the reset characteristic of the stage. For
1MRK 506 382-UEN A Section 7
Current protection
Line distance protection REL650 2.2 IEC 213
Technical manual
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