Siemens 7SG16 Ohmega Distance Protection
Answers for energy
Product Overview
The Siemens 7SG16 Ohmega range of numeric distance relays combines advanced microprocessor technology with proven impedance measuring techniques. These relays provide full scheme distance protection using mho or quadrilateral elements, offering superior fault coverage through continuous monitoring of all fault loops and zones. The distance protection is enhanced by integrated signalling schemes, allowing application as unit protections. The range includes various protection and control features tailored for different applications, with IEC 60870 standard communications for remote settings, instrumentation, waveform storage, and data collection.
The 7SG163n series is designed for distribution networks, while the 7SG164n series is suitable for sub-transmission networks.
Image Description: A front view of the Siemens 7SG16 Ohmega relay unit, featuring a display screen, control buttons (ENTER, CANCEL), and numerous status indicator LEDs labeled with protection functions such as ZONE 1, ZONE 2, ZONE 3, EARTH, SOTF, etc.
The relays incorporate self-monitoring features, including hardware and software watchdogs and data integrity checks, to ensure correct operation.
Functional Overview
Standard Features:
- 3-zone distance protection with mho characteristics and earth fault compensation.
- Voltage Transformer (VT) supervision to detect blown VT fuses by monitoring voltage and current sequence components.
- Switch on to Fault (SOTF) protection for fast tripping when the circuit breaker closes with earthing clamps in place.
- Transient-free Highset overcurrent protection.
- Power swing detection, which can be configured to block distance protection tripping.
- Fault locator providing fault location in miles, kilometres, or line percentage.
- Permissive underreach and permissive overreach signalling schemes.
- Time-stepped operation.
- Trip circuit supervision.
Optional Features:
- 4th distance protection zone.
- Quadrilateral characteristics for earth fault.
- Single-pole tripping.
- Blocking, acceleration, and loss of load schemes.
- Stub protection.
- Directional Earth-Fault (DEF) protection (single or dual) for high resistance earth faults, with Permissive Overreach and Blocking signalling schemes.
- Sensitive Earth-Fault protection.
- Autoreclose (high-speed single-pole or three-pole) with Reach extension scheme.
- Check synchronising.
- Overvoltage and undervoltage protection.
Monitoring Functions
Analogue values can be displayed in primary or secondary quantities on the LCD screen, including:
- Primary current per phase
- Primary earth current
- Secondary current per phase
- Secondary earth current
- Primary phase voltages
- Secondary voltages
- Apparent power and power factor
- Real and reactive power
- Direction
Other monitored parameters include:
- Autoreclose status
- Check sync line and bus voltages
- Check sync differential voltage
- Check sync phase difference
- Bus and line frequency
- Check sync slip frequency
- Output contacts status
- Status inputs
- Trip counters
- Number of waveform and event records stored
- Time and Date
LED Indication: 32 user-programmable LEDs are available to indicate fault and alarm status.
Detailed Functionality
Description of Functionality:
The 7SG16 relays utilize proven phase comparator techniques to deliver full scheme distance protection with mho and quadrilateral characteristics. All fault loops and zones are continuously measured, eliminating the need for starter characteristics and ensuring correct clearance of developing faults. Reach settings for each zone are independent for phase and earth fault protection, with separate time delays configurable for each zone. The distance protection can directly trip the circuit breaker (CB) or use a signalling scheme to verify a trip decision. Some models incorporate signalling schemes such as current reversal detection, circuit breaker echo, and weak infeed detection for enhanced operational reliability.
Power Swing: System power swings can cause apparent impedance drops due to heavy load variations or remote faults, potentially leading to unintended protection operation. The relay detects power swings using two dedicated impedance characteristics that encompass protection zones. A fault causes rapid pick-up of both elements, while a power swing results in a longer delay between the outer and inner element pick-up. Power swing detection can inhibit distance protection tripping.
Switch on to Fault (SOTF): This function provides instantaneous fault clearance when the circuit breaker is inadvertently closed with earthing clamps still in place, causing a 3-phase short circuit. Two SOTF styles are available: AC SOTF for line VTs and DC SOTF for bus VTs.
Voltage Transformer Supervision: To prevent unwanted operations due to loss of VT supply, the relay monitors sequence component voltages. During healthy conditions, no residual or NPS voltage is present. If a VT fuse fails, residual and NPS voltage appear without a corresponding increase in sequence current, triggering VT supervision for an alarm. This function can also inhibit distance protection operation.
Circuit Breaker Fail (50BF): This function monitors current after a trip signal. If the current does not cease within a specified interval, an output is generated, which can be used to backtrip an upstream circuit breaker. The function features a fast reset.
Optional Functionality:
- Phase-fault (highset) overcurrent: A transient-free, definite-time overcurrent element with a DTL characteristic.
- Directional earth-fault (DEF): Provides effective clearance of high impedance earth faults. It includes a directional element (operating from residual current and voltage) and an overcurrent element (operating from residual current). A second DEF element can detect faults in forward and reverse directions. Various signalling schemes are available for DEF protection.
- Sensitive earth-fault (SEF): A non-directional protection operating from residual current, settable down to 2% of nominal current for very high impedance earth faults. A definite-time delay allows grading with distance protection.
- Overvoltage and undervoltage: Two overvoltage and two undervoltage elements are available with definite-time delays, monitoring line voltages for alarm and trip levels.
- Autoreclose: Integrated autorecloser provides delayed or high-speed autoreclose after a zone 1 or scheme-generated trip. The 7SG163n offers single-shot three-pole autoreclose, while the 7SG164n supports up to two reclosing shots with various single- and three-pole sequences.
- Check Synchronising: Ensures the circuit breaker is only closed when power systems are synchronized.
Application Schemes
Various application schemes are supported:
- Time Stepped Distance: Utilizes time-delayed Zones 2, 3, and 4, with optional direct intertripping.
- Permissive Underreach (PUR): Zone 1 provides instantaneous coverage up to 80% of the line length, with aided tripping using accelerated Zone 3 (7SG163n) or Zone 2 (7SG164n) for the remaining 20%.
- Zone 2 Accelerated (PA): Zone 1 offers instantaneous coverage up to 80% of the line length, with aided tripping using accelerated Zone 2 for the remaining 20%.
- Blocking Overreach Type 2 (Zone 4): Zone 2 is set to overreach, providing instantaneous coverage over 100% of the line length. This is blocked for out-of-zone faults by the remote Zone 4 reverse element.
- Permissive Overreach Type 2 (POR2): Zone 2 overreaches to provide instantaneous coverage of 100% of the line length, aided by a permissive signal from the remote Zone 2.
- Blocking Overreach Type 1 (without Z4): Zone 2 overreaches to cover 100% of the line length, blocked for out-of-zone faults by the remote Z3/Z2 elements.
- Reach extension (RE): Provides instantaneous coverage up to an extended Zone 1 setting for the first fault, with delayed stepped distance for persistent faults. For relays with autoreclose, Zone 1 coverage is extended for the initial fault.
- DEF Permissive Overreach (DPOR): Overreach Directional Earth Fault (DEF) provides short-time delayed coverage over 100% of the line length for earth faults, using a permissive signal from the remote DEF.
- Current Reversal Logic: This logic is employed with permissive overreach schemes on dual circuit lines. It prevents false tripping of a healthy adjacent feeder that might occur due to sudden reversal of fault current caused by the tripping of the faulted feeder.
Diagram Description: Illustrates time-delayed zones (Z1A, Z2A, Z3A for Relay A; Z1B, Z2B, Z3B for Relay B) connected via a signalling link, showing the application of time-delayed distance protection.
Diagram Description: Depicts zones and a signalling link, showing Zone 1 coverage up to 80% and aided tripping for the remaining portion.
Diagram Description: Similar to PUR, illustrating Zone 1 coverage and accelerated Zone 2 aiding.
Diagram Description: Shows relays A and B with zones including Z4B. Zone 2 of Relay A overreaches and is blocked by the remote Zone 4 element of Relay B.
Diagram Description: Illustrates overreaching Zone 2 of Relay A receiving a permissive signal from Zone 2 of Relay B.
Diagram Description: Shows Zone 2 of Relay A overreaching and being blocked by the remote Z3/Z2 elements of Relay B.
Diagram Description: Depicts extended Zone 1 coverage for the first fault, with subsequent faults handled by time-stepped distance.
Diagram Description: Illustrates DEF protection with overreach and a permissive signal for earth faults.
Data Storage and Communication
- Sequence of Event Records: Up to 500 events are stored with 1ms time resolution and are accessible via communications.
- Fault Records: The last 10 fault records, including time, date of trip, measured quantities, and fault type, are available from the fascia.
- Disturbance Recorder: A waveform recorder can be triggered by a protection function or external input, featuring a configurable pre-fault trigger. Up to 10 fault waveforms, along with associated analogue and digital values, can be stored.
- Communications: The relay features two fibre-optic communication ports (BFOC/2.5 ST connectors) and an RS232 port for local laptop interrogation. Data communication is compliant with the IEC 60870-5-103 standard.
Image Description: A screenshot of the "Reydisp Evolution" software interface, showing a "Data Header Window" with plots of signals like "W1 Ia", "W1 Ib", "W1 Ic" over time, along with digital signal indicators. It displays waveform data and associated parameters.
Reydisp Evolution: This software is common across the Reyrolle numeric product range and is used for applying settings, interrogating settings, and retrieving disturbance waveforms. It utilizes the IEC 60870-5-103 protocol.
Technical Data
For comprehensive technical data, refer to the Performance Specification of the Technical Manual.
| Reference Conditions | Value |
|---|---|
| General (IEC60255 Parts 6, 6A & 16) | Nominal |
| Auxiliary | Nominal |
| Frequency | 50Hz |
| Ambient Temperature | 20°C |
| Impedance setting | 6 Ohms |
| Line angle | 75° |
| Z0/Z1 | 2.5 |
| Accuracy Influencing Factors | Specification |
|---|---|
| Temperature | 10 °C to +55 °C: ≤5% variation |
| Frequency | 47 Hz to 52 Hz: Setting: ≤5% variation |
| 57 Hz to 62 Hz: Operate Time: ≤5% variation |
| Parameter | Specification |
|---|---|
| ZN setting | 0.1 to 250 Ω |
| N Angle | 0 to 90° step 5° |
| Accuracy (ZN = 6Ω, mho characteristic, 3-phase fault) | |
| ZN1 (Φ =ΦN ± 3°) | ZN ± 5% or 0.1 Ω for SIR <30 |
| ZN ± 10% or 0.1 Ω for SIR ≥30 | |
| Z (Φ =ΦN ± 10°) | ZN1 x cos(ΦN -Φ) ± 0.05ZN Ω |
| Z (0° ≤ Φ ≤ 90°) | ZN1 x cos(ΦN -Φ) ± 0.1ZN Ω |
| Accuracy (all ZN) | Class index plus an error not exceeding class index |
| Transient overreach | Class index plus an error not exceeding class index |
| Operating time (see Technical Manual) | min. 17ms (7SG164n) / min. 35ms (7SG163n) |
| Delay (additional to operating time) | 0 to 10 s step 10 ms |
| Accuracy | Setting ± 1% or 10 |
| Characteristic | DTL |
|---|---|
| Level | 0.05 to 4.00 x In |
| Settings | Operate: Setting ± 5% / Reset: ≥95% of operate level |
| Accuracy | Setting ± 1% or 5ms |
| Delay | 0 to 20s steps 1ms |
| Characteristic | DTL |
|---|---|
| Level | 0.1 to 35.0 x In |
| Settings | Operate: Setting ± 5% / Reset: ≥95% of operate level |
| Accuracy | Setting ± 1% or 10ms |
| Delay | 0 to 1000ms |
Inputs and Outputs
| Characteristic energising quantity | Performance data To IEC 60255-3 |
|---|---|
| AC Current/Voltage | 1A, 2A or 5A, 3-phase / 63.5V line-neutral, 3-phase |
| Frequency | 50/60Hz |
| Nominal Voltage | Operating Range V dc |
|---|---|
| 30V | 18 to 37.5V |
| 48V | 37.5 to 60V |
| 110 V | 87.5 to 137.5V |
| 220V | 175 to 280V |
Note: The binary input voltage need not be the same as the main energising voltage.
| Parameter | Value |
|---|---|
| Minimum DC current for operation (30V and 48V inputs only) | 10 mA |
| Reset/Operate Voltage Ratio | ≥ 90% |
| Typical response time | < 5 ms |
| Typical response time when used to energise an output relay contact | < 15 ms |
| Minimum pulse duration | 40 ms |
Binary inputs will not respond to the following: 250V RMS 50/60 Hz applied for two seconds through a 0.1μF capacitor; 500 V RMS 50/60 Hz applied between each terminal and earth; Discharge of a 10μF capacitor charged to maximum DC auxiliary supply voltage.
| Thermal Withstand | Specification |
|---|---|
| 12A | continuous |
| 15A | 10 minutes |
| 30A | 2 minutes |
| 240A | 2 Seconds |
| 340A | 1 Second |
| 625A peak | 1 Cycle |
| Burden | Specification |
|---|---|
| 5A | ≤ 0.625 VA |
| 1A | ≤ 0.1 VA |
| ≤ 0.025 VA |
Note: Burdens are measured at nominal rating.
| Parameter | Specification |
|---|---|
| Thermal Withstand | 3.5 x Vn |
| Burden | ≤ 0.01 VA |
Note: Burdens are measured at nominal rating.
| Nominal Voltage | Operating Range V dc |
|---|---|
| 30V | 24 to 37.5V |
| 48/110V | 37.5 to 137.5 |
| 220 V | 178.0 to 280.0 |
| 110/220V | 88 to 275 |
| Parameter | Burden |
|---|---|
| Operate State | 15 W |
| Quiescent (Typical) | |
| Maximum | 27 W |
| Specification | Value |
|---|---|
| Carry continuously | 5A ac or dc |
| Make and carry (L/R ≤ 40 ms and V ≤ 300V) | 20A ac or dc for 0.5s / 30A ac or dc for 0.2s |
| Breaking Capacity (≤ 5A and ≤ 300 V): | |
| AC Resistive | 1250 VA |
| AC Inductive | 250 VA at p.f. ≤ 0.4 |
| DC Resistive | 75 W |
| DC Inductive | 30 W at L/R ≤ 40ms / 50 W at L/R ≤ 10ms |
| Minimum number of operations | 1000 at maximum load |
| Minimum recommended load | 0.5 Watt limits 10mA or 5V |
Mechanical, Electrical, and Environmental Specifications
| Specification | Value |
|---|---|
| Vibration (Sinusoidal) IEC 60255-21-1 Class 1 | 0.5 gn, Vibration response / 1.0 gn, Vibration endurance: ≤5% variation |
| Shock Bump IEC 60255-21-2 Class 1 | 5 gn, Shock response, 11ms / 15 gn, Shock withstand, 11ms / 10 gn, Bump test, 16ms: ≤5% variation |
| Seismic IEC 60255-21-3 Class 1 | 1 gn, Seismic response: ≤5% variation |
| Durability | In excess of 106 operations |
| Specification | Value |
|---|---|
| IEC 60255-22-3 | 10 V/m, 80 to 1000 MHz: ≤5% variation |
| IEC 60255-22-6 | 10 V, 0.15 to 80 MHz: ≤5% variation |
| Frequency Range | Limits dB(µV) | |
|---|---|---|
| Quasi-peak | Average | |
| 0.15 to 0.5 MHz | 79 | 66 |
| 0.5 to 30 MHz | 73 | 60 |
| Frequency Range | Limits at 10 m Quasi-peak, dB(µV/m) |
|---|---|
| 30 to 230 MHz | 40 |
| 230 to 10000 MHz | 47 |
| Specification | Value |
|---|---|
| Insulation IEC 60255-5 RMS levels for 1 minute | Between all terminals and earth: 2.0 kV / Between independent circuits: 2.0 kV / Across normally open contacts: 1.0 kV |
| Transient Overvoltage IEC 60255-5 | Between all terminals and earth or between any two independent circuits without damage or flashover: 5 kV (1.2/50 µs), 0.5 J |
| High Frequency Disturbance IEC 60255-22-1 Class III | 2.5kV, Longitudinal mode / 1.0kV, Transverse mode: ≤3% variation |
| Electrostatic Discharge IEC 60255-22-2 Class III | 8kV, Contact discharge: ≤5% variation |
| Fast Transient IEC 60255-22-4 Class IV | 4kV, 5/50ns, 2.5 kHz, repetitive: ≤3% variation |
| Specification | Value |
|---|---|
| Temperature IEC 60068-2-1/2 | Operating: -10 °C to +55 °C / Storage: -25 °C to +70 °C |
| Humidity IEC 60068-2-3 | Operational test: 56 days at 40 °C and 93% RH |
Case Dimensions
The 7SG16 Ohmega is available in two case sizes:
E12 Case Dimensions:
Diagram Description: Shows the panel cut-out dimensions (295.25mm width, 204.25mm height) and overall dimensions (311.5mm width, 168mm height) for the E12 case, including clearances for wiring and fiber optic cables.
E16 Case Dimensions:
Diagram Description: Shows the panel cut-out dimensions (364mm width, 273mm height) and overall dimensions (415.5mm width, 168mm height) for the E16 case, including clearances for wiring and fiber optic cables.
Notes on mounting holes indicate suitability for M4 thread forming screws in ferrous/aluminium panels (1.6mm thick and above), or M4 clearance holes with machine screws, nuts, and lockwashers for other panel types.
Connection Diagram
Diagram Description: A detailed connection diagram illustrating the rear panel layout of the 7SG16 Ohmega relay. It shows the arrangement of terminals for power supply (PSU), CPU, optical modules (Opt), and input/output (I/O) modules. Terminal connections for output relays (RL 1-29) and status inputs (SI 1-27) are detailed, alongside connections for current transformers (CTs) and voltage transformers (VTs), including auxiliary CT and auxiliary voltage inputs. Notes clarify the usage of specific inputs and optional modules. It also depicts the direction of power flow.
Ordering Information
The 7SG16 Ohmega is available in different series (300 and 400) with various configurations for protection options, auxiliary supply, I/O range, frequency, nominal current, voltage inputs, housing size, and communication interface. Each combination corresponds to a specific order number.
Ohmega (300 series)
Standard Functionality: Numeric distance protection with integrated standard functions, supporting 1, 2, and 5A inputs and IEC60870-5-103 communications. Includes Distance Protection (21/21N) with mho characteristics, loss of load, power swing blocking, SOTF, fault locator, and various signalling schemes (time-stepped, permissive underreach/overreach, accelerated underreach, current reversal, CB echo, weak infeed). Auxiliary functions include VT supervision, phase-fault overcurrent, and trip circuit supervision.
Relay Specific Functionality:
- OHMEGA 305: 3 mho impedance zones.
- OHMEGA 308: 3 mho impedance zones, earth-fault quadrilateral characteristics, Directional (high impedance) earth-fault (67N), IDMTL direct tripping and permissive overreach schemes, current reversal and CB echo, single shot auto-reclose (79), check synchronising (25), sensitive earth-fault (50G), power swing blocking (68), two stage DTL undervoltage (27), two stage DTL overvoltage (59).
- OHMEGA 311: 3 mho impedance zones, Directional (high impedance) earth-fault (67N), IDMTL direct tripping and permissive overreach schemes, current reversal and CB echo, single shot auto-reclose with reach extension (79), check synchronising (25), broken conductor, circuit breaker fail (50BF).
- OHMEGA 314: 4 mho impedance zones, earth-fault quadrilateral characteristics, blocking overreach, dual directional (high impedance) earth-fault (67N), IDMTL direct tripping and permissive overreach schemes, blocking scheme, current reversal, CB echo, weak infeed, single shot auto-reclose with reach extension (79), check synchronising (25), sensitive earth-fault (50G), two stage DTL undervoltage (27), two stage DTL overvoltage (59).
- OHMEGA 315: 4 mho impedance zones, earth-fault quadrilateral characteristics, overcurrent guard, blocking overreach, dual directional (high impedance) earth-fault (67N), IDMTL direct tripping and permissive overreach schemes, blocking scheme, current reversal, CB echo, weak infeed, single shot auto-reclose with reach extension (79), check synchronising (25), sensitive earth-fault (50G), two stage DTL undervoltage (27), two stage DTL overvoltage (59).
Auxiliary Supply / Binary Input Voltage Options: Various combinations of DC auxiliary supply and binary input voltages are available (e.g., 30V DC, 48/110V DC, 220V DC) with different binary input burdens.
I/O Range Options: Different configurations for Binary Inputs / Binary Outputs are available (e.g., 11 Inputs / 13 Outputs, 19 Inputs / 21 Outputs, 27 Inputs / 29 Outputs).
Frequency: 50Hz or 60Hz.
Nominal Current: 1, 2, or 5 A.
Voltage Inputs: 63/110 V AC.
Housing Size: E12 (4U high, 4U wide vertical) or E16 (4U high, 4U wide vertical).
Communication Interface: Fibre optic (ST-connector) / IEC 60870-5-103.
Ohmega (400 series)
Standard Functionality: Numeric distance protection for sub-transmission networks, with integrated standard functions, supporting 1, 2, and 5A inputs and IEC60870-5-103 communications. Includes Distance Protection (21/21N) with four mho impedance zones, phase and earth-fault mho characteristics, power swing blocking, SOTF, fault locator, and signalling schemes (time-stepped, permissive underreach/overreach, blocking overreach). Auxiliary functions include VT supervision and phase-fault overcurrent.
Relay Specific Functionality:
- OHMEGA 402: Distance Protection (21/21N), three pole tripping, stub protection.
- OHMEGA 406: Distance Protection (21/21N), earth-fault quadrilateral characteristics, single pole tripping, loss of load, stub protection, current reversal, CB echo, weak infeed, Directional (high impedance) earth-fault (67N), DTL direct tripping and permissive overreach schemes, current reversal and CB echo, weak infeed, two shot 1P/3P auto-reclose with reach extension (79), check synchronising (25).
- OHMEGA 408: Distance Protection (21/21N), earth-fault quadrilateral characteristics, single pole tripping, current reversal, CB echo, weak infeed, thermal overload.
Auxiliary Supply / Binary Input Voltage Options: Various combinations of DC auxiliary supply and binary input voltages are available.
I/O Range Options: Different configurations for Binary Inputs / Binary Outputs are available.
Frequency: 50Hz or 60Hz.
Nominal Current: 1, 2, or 5 A.
Voltage Inputs: 63/110 V AC.
Housing Size: E12 (4U high, 4U wide vertical) or E16 (4U high, 4U wide vertical).
Communication Interface: Fibre optic (ST-connector) / IEC 60870-5-103.
Contact Information
Published by and copyright © 2010: Siemens AG, Energy Sector, Freyeslebenstrasse 1, 91058 Erlangen, Germany.
Siemens Protection Devices Limited, P.O. Box 8, North Farm Road, Hebburn, Tyne & Wear, NE31 1TZ, United Kingdom.
Website: www.siemens.com/energy
For more information, contact Customer Support Center:
Phone: +49 180/524 70 00 (Charges depending on provider)
Fax: +49 180/524 24 71
E-mail: support.energy@siemens.com
Order No. E53000-K7076-C5-1. Printed in Fürth.
