Figure 4-30. Volts per Hertz Overexcitation Logic Block
The integrating time characteristic closely approximates the heating characteristic of the protected
equipment as overexcitation increases. A linear reset characteristic provides for the decreasing (cooling)
condition.
The 24 element is enabled or disabled by the
Mode
input. Two modes are available. Selecting Mode 0
disables protection; Mode 1 enables the 24 element.
The block (
BLK
) input is used to disable protection. A BESTlogic expression defines how the
BLK
input
functions. When this expression is TRUE, the element is disabled by forcing the outputs to logic 0 and
resetting the timers. This feature functions in a similar way to the torque control contact of an
electromechanical relay.
Theory of Operation for Volts per Hertz Overexcitation
V/Hz protection responds to the magnitude of voltage versus frequency where the measured voltage is
phase-phase and includes the phase with the frequency measurement element. If monitored V/Hz is
above a pickup setting, the pickup bit is asserted and integrating and/or definite time timers start timing
towards trip. The trip output becomes TRUE when the first timer times out (integrating or definite time
characteristic). If monitored V/Hz is above both the integrating and definite time pickup thresholds, the
definite time delay has priority over the integrating time characteristic.
The pickup settings determine the V/Hz pickup level. The measured V/Hz is always calculated as the
measured voltage divided by the sensed system frequency. The measured phase depends on the
sensing voltage setting, SG-VTP. The 24 function monitors VAB for both 3-wire and 4-wire connections.
Thus, setting is in VPP/Hz for VT connection = 3W, 4W, AB, BC, CA and VPN/Hz for VT connection =
AN, BN, CN. For more information, refer to Section 3,
Input and Output Functions
.
Nominal voltage for the BE1-CDS-240 is defined as a phase to neutral quantity. (Refer to Section 3,
Input
and Output Functions
, for details). Nominal V/Hz depends on the sensing voltage (VT) connection,
nominal voltage, and nominal frequency settings. Nominal V/Hz is calculated as the nominal voltage
divided by nominal frequency. For VT connections equal to 3W, 4W, AB, BC, CA, the nominal voltage
(phase-neutral value) must be converted to a phase-phase value by multiplying by the square root of 3.
No additional conversion is required for VT connections equal to AN, BN, or CN.
For 3W, 4W, AB, BC, or CA phase to phase sensing connections:
Frequency
Nominal
3
V
V/Hz
Frequency
Measured
V
Measured
V/Hz
Nominal
Nominal
Phase
-
Phase
Measured
For AN, BN, or CN phase to neutral sensing connections:
Frequency
Nominal
V
V/Hz
Frequency
Measured
V
Measured
V/Hz
Nominal
Nominal
Neutral
-
Phase
Measured
Equations 4-13 and 4-14 represent the trip time and reset time for a constant V/Hz level. Normally, the
V/Hz pickup is set to a value greater than the V/Hz nominal. This ensures that V/Hz measured divided by
V/Hz nominal is always greater than 1.000 throughout the pickup range. If the pickup is set less than
nominal, then measured values above pickup and below nominal will result in the maximum time delay.
The maximum time delay is determined by Equation 4-13 with (V/Hz measured / V/Hz nominal) set equal
to 1.001. The overall inverse time delay range is limited to 1,000 seconds maximum and 0.2 seconds
minimum.
4-36
BE1-CDS240 Protection and Control
9365200990 Rev F
Summary of Contents for BE1-CDS240
Page 2: ......
Page 8: ...vi BE1 CDS240 Introduction 9365200990 Rev F This page intentionally left blank ...
Page 38: ...1 28 BE1 CDS240 General Information 9365200990 Rev F This page intentionally left blank ...
Page 40: ...ii BE1 CDS240 Quick Start 9365200990 Rev F This page intentionally left blank ...
Page 152: ...ii BE1 CDS240 Metering 9365200990 Rev F This page intentionally left blank ...
Page 226: ...iv BE1 CDS240 Application 9365200990 Rev F This page intentionally left blank ...
Page 286: ...ii BE1 CDS240 Security 9365200990 Rev F This page intentionally left blank ...
Page 290: ...9 4 BE1 CDS240 Security 9365200990 Rev F This page intentionally left blank ...
Page 292: ...ii BE1 CDS240 Human Machine Interface 9365200990 Rev F This page intentionally left blank ...
Page 306: ...10 14 BE1 CDS240 Human Machine Interface 9365200990 Rev F This page intentionally left blank ...
Page 308: ...ii BE1 CDS240 ASCII Command Interface 9365200990 Rev F This page intentionally left blank ...
Page 342: ...11 34 BE1 CDS240 ASCII Command Interface 9365200990 Rev F This page intentionally left blank ...
Page 349: ...Figure 12 5 Horizontal Rack Mount Front View 9365200990 Rev F BE1 CDS240 Installation 12 5 ...
Page 361: ...Figure 12 17 Typical DC Connection Diagrams 9365200990 Rev F BE1 CDS240 Installation 12 17 ...
Page 372: ...12 28 BE1 CDS240 Installation 9365200990 Rev F This page intentionally left blank ...
Page 468: ...13 92 BE1 CDS240 Testing and Maintenance 9365200990 Rev F This page intentionally left blank ...
Page 512: ...14 42 BE1 CDS240 BESTCOMS Software 9365200990 Rev F This page intentionally left blank ...
Page 544: ...ii BE1 CDS240 Terminal Communication 9365200990 Rev F This page intentionally left blank ...
Page 550: ...ii BE1 CDS240 Settings Calculations 9365200990 Rev F This page intentionally left blank ...
Page 578: ...D 28 BE1 CDS240 Settings Calculations 9365200990 Rev F This page intentionally left blank ...
Page 579: ......