Comparison of Protection Relay types
Comparison Table
This comparison summarize characteristics of all protection relay types described in previously published technical articles:
| Characteristic | El. Mech. Relay | Static Relay | Digital Relay | Numerical Relay |
| Technology Standard | 1st generation relays. | 2nd generation relays. | Present generation relays. | Present generation relays. |
| Operating Principle | They use principle of electromagnetic principle. | In this relays transistors and IC’s been used | They use microprocessor. Within built software with predefined values | They use microprocessor. Within built software with predefined values |
| Measuring elements/ Hardware | Induction disc, electromagnets, induction cup, balance beam | R, L, C, transistors, analogue ICs comparators | Microprocessors, digital ICs, digital dignal processors | Microprocessors, digital ICs, digital signal processors |
| Measuring method | Electrical qtys converted intomechanical force, torque | Level detects,comparison withreference value in analogue comparator | A/D conversion, numerical algorithm techniques | A/D conversion, numerical algorithm techniques |
| Surrounding Environment | Depend upon gravitation and the value changes to the surrounding magnetic fields also. | There value may vary with respect to temperature also. | ||
| Characteristic | El. Mech. Relay | Static Relay | Digital Relay | Numerical Relay |
| Relay Size | Bulky | Small | Small | Compact |
| Speed of Response | Slow | Fast | Fast | Very fast |
| Timing function | Mechanical clock works, dashpot | Static timers | Counter | Counter |
| Time of Accuracy | Temp. dependant | Temp. dependant | Stable | Stable |
| Reliability | High | Low | High | High |
| Vibration Proof | No | Yes | Yes | Yes |
| Characteristics | Limited | Wide | Wide | Wide |
| Requirement of Draw Out | Required | Required | Not required | Not required |
| CT Burden | High | Low | Low | Low |
| CT Burden | 8 to 10 VA | 1 VA | < 0.5 VA | < 0.5 VA |
| Characteristic | El. Mech. Relay | Static Relay | Digital Relay | Numerical Relay |
| Reset Time | Very High | Less | Less | Less |
| Auxiliary supply | Required | Required | Required | Required |
| Range of settings | Limited | Wide | Wide | Wide |
| Isolation Voltage | Low | High | High | High |
| Function | Single function | Single function | Multi function | Single function |
| Maintenance | Frequent | Frequent | Low | Very Low |
| Resistance | 100 mille ohms | 10 Ohms | 10 Ohms | 10 Ohms |
| Output Capacitance | < 1 Pico Farad | > 20 Pico Farads | > 20 Pico Farads | > 20 Pico Farads |
| Characteristic | El. Mech. Relay | Static Relay | Digital Relay | Numerical Relay |
| Deterioration due to Operation | Yes | No | No | No |
| Relay Programming | No | Partially | Programmable | Programmable |
| SCADA Compatibility | No | No | Possible | Yes |
| Operational value indication | Not Possible | Possible | Possible | Possible |
| Visual indication | Flags, targets | LEDs | LEDs, LCD | LEDs, LCD |
| Self monitoring | No | Yes | Yes | Yes |
| Parameter setting | Plug setting, dial setting | Thumb wheel, dual in line switches | Keypad for numeric values, through computer | Keypad for numeric values, through computer |
| Fault Disturbance Recording | Not possible | Not possible | Possible | Possible |
