Sel -421-4 Manual

SEL-421-4, -5 Protection,
Automation, and Control System
High-Speed Line Protection,
Automation, and Control System
Key Features and Benefits
The SEL-421-4, -5 Protection, Automation, and Control System combines high-speed distance and directional protec-
tion with complete control for a two-breaker bay.
➤
Complete Distance Protection. You can apply as many as five zones of phase and ground distance and directional
overcurrent elements. Select mho or quadrilateral characteristics for any phase or ground distance element. Use the
optional high-speed distance elements and series-compensation logic to optimize protection for critical lines or
series-compensated lines. Patented coupling capacitor voltage transformer (CCVT) transient overreach logic
enhances the security of Zone 1 distance elements. Best Choice Ground Directional Element
directional element performance and eliminates the need for many directional settings. Apply the distance and
directional elements in communications-based protection schemes such as POTT, DCB, and DCUB, or for
instantaneous or time-step backup protection.
➤
Power Swing Blocking and Out-of-Step Tripping. You can select power swing blocking of distance elements for
stable power swings or out-of-step tripping for unstable power swings. Zero-setting, out-of-step detection logic is
available, eliminating the need for settings and power system studies.
➤
Switch-Onto-Fault. Disconnect status inputs and voltage elements can enable high-speed protection.
➤
Synchronism Check. Synchronism check can prevent circuit breakers from closing if the corresponding phases
across the open circuit breaker are excessively out of phase, magnitude, or frequency. The synchronism-check
function has a user-selectable synchronizing voltage source and incorporates slip frequency, two levels of maximum
angle difference, and breaker close time into the closing decision.
➤
Reclosing Control. You can incorporate programmable single-pole or three-pole trip and reclose of one or two
breakers into an integrated substation control system. Synchronism and voltage checks from multiple sources
provide complete bay control.
➤
Fault Locator. Utilities can efficiently dispatch line crews to quickly isolate line problems and restore service
faster.
Schweitzer Engineering Laboratories, Inc.
®
logic optimizes
SEL-421-4, -5 Data Sheet