With advancement in technology, ElectroMechanical Relays are replaced by Numerical relays. Here we explain WHY & HOW Numerical Relays are better than ElectroMechanical Relays.

2. Spring
Disc
Time Adjustment:
Tension controlled
Contacts
Core
Sensing Coil
Electro Mechanical (Start of Century)

3. -controller
Current SamplingB CA E
AC - DC
Conversion
Output Control
Steady state data
Relay Contacts
Crystal
Micro Controller Based (Late 80s)

4. -controller
Current SamplingB CA E
Direct AC
Sampling
Output Control
Steady state data
Relay Contacts
Crystal Serial Port To Outside world
A to D
Late 90s: Numerical Relay Technology

5. Disadvantages
• No Phase Angle information.
• No Frequency information.
Time Domain Representation
Time
Amplitude
Frequency
50Hz
Frequency Domain Representation
Numerical Relay

6. Electro Mechanical Relay
• It works on Mechanical Parts, Springs and their appropriate tensions, which are
temperature dependent for giving Protection Trip Accuracy
• It needs to be Periodically Removed, Cleaned & need to do Spring Adjustments with
Season Changes for Correct Tripping Time Results
Numerical Relay
• Above problems are eliminated since No Moving Parts
• All IDMT timings, High Set Tripping Timings are with software based CPU
• CPU is completely embedded & gives Microsecond Repeat Accuracy
• No Periodical services, adjustments etc. required
Why do we recommend Numerical Relay?

7. Electro Mechanical Relay
• Generally Electro-Mechanical Relays are separately used for individual Phases
• High Set Setting is having different mechanism
• It consumes more space in Panels which increases C&R Panel cost
Numerical Relay
• All Numerical Relays are compact in size
• All Protection functions are available in same relay
• The Numerical Relay is 20% in size of Electro-Mechanical Relays of same functionality
Why do we recommend Numerical Relay?

8. Electro Mechanical Relay
• Memory of previous Fault records, Actual Value of Fault Current, etc. are not possible
to store
• Only one Mechanical Flag is shown for Relay Operation & Phase Indication
Numerical Relay
• Numerical Relays have the Memory to store the events & last 5 faults with Date &
Time Stamping
• This information is very important to diagnose Fault Pattern, by which Relay can be
reset so that such fault possibility could be removed/eliminated
• This information helps to get uninterrupted Power Supply which helps in good
Revenue Earning for the Utility
Why do we recommend Numerical Relay?

9. Electro Mechanical Relay
• Electro-Mechanical Relays are non-communicable
• These relays cannot be used for Sub Station Automation & SCADA system
Numerical Relay
• Numerical Relays are Communicable with all Standard Protocols
• Numerical Relays can be used for Sub Station Automation & SCADA system effectively
Why do we recommend Numerical Relay?

10. Numerical Self Power Relay

11. Integrated Solutions:
Protection & Automation
• Protection Relays
• SAS SCADA
• Control & Relay Panels
• Traction Protection

12. THANK YOU
Web: www.ashidaelectronics.com Email: sales@ashidaelectronics.com