Siemens SIPROTEC 5 Replacement and Upgrade Guide

Siemens SIPROTEC 5 Replacing Old Protective Devices: A Complete Guide to Migrating from SIPROTEC 4

Introduction: Why is it necessary to replace old protective devices

In the field of power system protection, the discontinuation of old protection devices, shortage of spare parts, and increasingly strict network security requirements are forcing operation and maintenance teams to seek modern upgrade solutions. The old modules of brands such as Woodward and Honeywell are facing the same dilemma, while the Siemens SIPROTEC 4 series is gradually being replaced by the new generation SIPROTEC 5. SIPROTEC 5 is based on a modular hardware and software platform, providing stronger protection functions, more flexible communication, and more comprehensive network security mechanisms. However, directly replacing the running SIPROTEC 4 device is not a simple "plug and play" - it is necessary to ensure that the line differential protection topology is not interrupted during the replacement process, and that the new and old devices can operate in a mixed manner. This article is based on Siemens' official technical documentation and elaborates on how to replace SIPROTEC 4 equipment with SIPROTEC 5, covering compatibility, hardware selection, engineering configuration, testing, and common troubleshooting.

Part 1: Compatibility Fundamentals of SIPROTEC 5 and SIPROTEC 4

1.1 Feasibility of Mixed Operations

Starting from firmware version V7.90, the SIPROTEC 5 line protection device supports mixed configuration with SIPROTEC 4 series devices for the first time. This means that during the replacement process, there is no need to replace all devices at once, and it can be gradually migrated. The two main application scenarios are as follows:

Scenario 1: Replace individual devices in the existing topology

Functionally remove an old SIPROTEC 4 device from the differential protection topology and upgrade it to SIPROTEC 5, while keeping the remaining devices in their original state, the entire differential protection can still operate normally.

Scenario 2: Expanding the existing SIPROTEC 4 topology

Add SIPROTEC 5 devices (supporting up to 6 endpoints) to the existing SIPROTEC 4 topology, enabling the system to have future scalability.

1.2 Supported Old Device Versions

According to Siemens technical documentation, the following SIPROTEC 4 models can be mixed with SIPROTEC 5 (V7.90 and above) for operation:

7SA522 / FF 4.70

7SA6 / EE 4.70

7SD52 / 53 / EE 4.70

7SD610 / DD 4.70

Earlier firmware versions are theoretically feasible, but have not been officially tested by Siemens. Therefore, before replacement, it is recommended to prioritize upgrading the SIPROTEC 4 device to the recommended version mentioned above.

1.3 Compatibility of Protection Interface Modules

Protection communication is the key to implementing differential protection and directional comparison protection for transmission lines. The existing communication converter on the SIPROTEC 4 side can be retained and only needs to be adapted on the SIPROTEC 5 side. The specific module requirements are as follows:

The SIPROTEC 5 side requires the use of USART-AD-1FO or USART-AE-2FO FOS modules, which can be directly connected via fiber optic cables.

For communication networks that comply with the IEEE C37.94 standard, subsequent versions will support the FO30 module.

When connecting long-distance modules FO17, FO18, and FO19, a suitable signal repeater should be used on the SIPROTEC 5 side.

This design allows users to utilize existing fiber infrastructure, significantly reducing replacement costs.

Part 2: Hardware Replacement Plan and Selection of Standard Variants

2.1 Understanding the modular hardware of SIPROTEC 5

SIPROTEC 5 equipment is divided into two categories:

Non modular devices (7xx82): such as 7SJ82, 7SA82, 7SD82, with a fixed width of 1/3 x 19 inches, cannot add expansion modules, but provide multiple pre configured standard variants.

Modular devices (7xx85/86/87 and 6MD8): such as 7SJ85, 7SA86, 7SD87, etc., support flexible increase in I/O volume through 1/6 width expansion modules, can configure up to 2 rows of hardware, and achieve up to 40 analog channels and over 200 binary I/O.

2.2 Standard variant selection for replacing SIPROTEC 4

For example, replacing the common SIPROTEC 4 line protection (such as 7SA6) with SIPROTEC 5 distance protection (7SA86), the following standard variants are recommended:

Recommended SIPROTEC 4 configuration: SIPROTEC 5 model standard variant binary input/output CT/VT quantity

Single CT, single VT, small amount of I/O 7SA86 Type 1 (1/3) 7 BI/14 BO 4I+4V

Multiple I/O requirements 7SA86 Type 8 (2/3) 31 BI/46 BO 4I+4V

Double circuit breaker wiring (breaker-a-half) 7SA86 Type 11 (5/6) 27 BI/33 BO 8I+8V

2.3 Current Transformer Terminals and Safe Replacement

SIPROTEC 5 adopts innovative "Safety CT Plug" technology. When replacing equipment, pulling out the current terminal will always keep the secondary circuit closed, completely avoiding the risk of CT open circuit. This feature is particularly important for uninterrupted replacement of old equipment. In addition, the rated value of the current transformer (1A/5A) can be electronically configured through software without the need to turn on the device or adjust jumpers.

Part 3: Using DIGSI 5 for Engineering Configuration and Parameter Migration

3.1 Offline Engineering and Online Synchronization of DIGSI 5

DIGSI 5 is a unified engineering tool for SIPROTEC 5, supporting the entire process from single line diagram design to equipment parameterization. When replacing old equipment, the following steps are recommended:

Generate product code using SIPROTEC 5 configurator

Select the device type, standard variant, and communication module on the Siemens website, and the system will automatically generate a unique product code. This code can be directly imported into DIGSI 5.

Create a project in DIGSI 5

After importing all SIPROTEC 5 devices, use the "Single Line Editor" to draw a system topology and graphically associate the protection function group with the actual primary devices (circuit breakers, CTs, VTs).

Migration protection setting

Although SIPROTEC 4 and SIPROTEC 5 have different fixed value formats, DIGSI 5 supports exporting CSV files from old projects, converting them, and then re inputting them. For distance protection, attention should be paid to the correspondence between the quadrilateral characteristic (Polygon) and the MHO characteristic.

3.2 Application Templates Acceleration Configuration

DIGSI 5 provides pre configured application templates for each device, such as:

Distance Protection Basic Template (Basic)

Distance protection of resonant grounding/arc suppression coil grounding system (including automatic reclosing)

Reactive distance protection (RMD) for overhead lines in grounding systems

RMD distance protection applicable to 1.5 circuit breaker wiring

After selecting the template, the system will automatically create the required functional groups (such as distance protection group, circuit breaker management group, fault recording group) and complete internal signal routing. Engineers only need to modify the fixed value and CT/VT ratio.

3.3 Configuration of Protection Communication

For differential protection or directional comparison protection, a protection interface needs to be configured. In DIGSI 5:

Add communication modules (such as USART-AE-2FO) to the device hardware tree

Select the "Protection Interface" application and set the communication type (Type 1 for differential protection, Type 2 for general data transmission)

Assign binary signals (such as trip permits and direction information) that need to be transmitted to the protection interface channel through the "Communication Mapping" editor

When performing mixed operations, the original communication converter settings remain unchanged on the SIPROTEC 4 side, while the corresponding fiber module and baud rate (64 kbit/s to 2 Mbit/s) are selected on the SIPROTEC 5 side.

Part Four: Testing and Troubleshooting

4.1 Offline verification using DIGSI 5 test suite

DIGSI 5 integrates a powerful testing suite that can verify protection functions without connecting a secondary tester:

Test sequence generator: It can create multi-step test sequences (such as simulating A-phase ground faults, three-phase short circuits), load them into the built-in test actuators of the device, and simulate analog and binary inputs in real time. This allows offline verification of all protection logic and automatic reclosing sequences before replacing the device.

Protection function test view: In distance protection testing, the position of the impedance trajectory falling in the characteristic circle or quadrilateral can be displayed in real time, and the start/trip signal can be recorded.

4.2 Necessary tests after on-site replacement

Hardware wiring test: Force close a relay output through DIGSI 5, observe the displacement of the binary input of the remote device, and verify the correct wiring of the inter interval interlock.

Loop Test for Protection Interface: Select the communication module interface, send the test message, receive it after remote loopback, and calculate the bit error rate and transmission delay. This test can diagnose the quality of fiber optic links.

Differential protection stability test: After a load operation of the equipment, use the phasor diagram of DIGSI 5 to compare the amplitude and phase of the current on this side and the opposite side, ensuring that the differential current is close to zero and the braking current is normal.

Circuit breaker failure protection transmission: Simulate protection startup and verify whether the circuit breaker failure protection (50BF) issues a re trip or bus trip command according to the set delay.

4.3 Common Troubleshooting

Possible causes and solutions for the fault phenomenon

New and old devices cannot establish protection communication module type mismatch (Type1 vs Type2) or communication parameter inconsistency. Check the interface types of both parties (USART-AE-2FO and SIPROTEC 4-side converter compatibility) and confirm that the baud rate and CRC check are consistent

Differential protection misoperation or refusal CT ratio setting error, incorrect vector group calibration in DIGSI 5 differential protection function group, input primary side rated current and wiring group (such as Yyn0), equipment automatically calculates compensation

After replacement, the frequency tracking abnormality did not activate the frequency tracking group. In the protection function group attribute, enable frequency tracking and assign all devices on the same line to the same tracking group

After Network Security Lockdown Role Access Control (RBAC) is activated, the engineering account is locked for emergency access function (resetting security settings through device panel or USB connection)

Part 5: Advanced Topic - Hybrid Operations and Redundant Communication for Protecting Interfaces

5.1 Hybrid differential protection topology of SIPROTEC 4 and SIPROTEC 5

When the A end of a line is still SIPROTEC 4 and the B end has been replaced with SIPROTEC 5, differential protection can still work normally. Key requirements:

Both ends must use the same protection interface type (synchronous HDLC)

The signal list in the communication mapping needs to be consistent (such as sending start signals, trip commands)

Supports up to 6 terminals, differential algorithm automatically adapts under mixed configuration

SIPROTEC 5 provides enhanced communication capabilities, such as:

Hot standby redundant link: When the primary fiber is interrupted, it automatically switches to the backup path with a switching time of less than 20ms.

Ring network self-healing: In a ring topology, a single point fiber breakage will be converted to a chain topology within 20ms, and differential protection will not be interrupted.

IEEE C37.94 Direct Connection: Can connect to SDH/MPLS networks without the need for external converters.

5.2 Analyze the behavior of the replaced system using a fault recorder (7KE85)

The 7KE85 fault recorder in the SIPROTEC 5 platform is a powerful tool for later validation of replacement projects. Its characteristics:

Up to 16kHz sampling rate, capable of capturing transient processes

Support continuous wave recording (Slow scan) and event triggered wave recording (Fast scan)

Can be triggered through IEC 61850 GOOSE and recorded synchronously with protection actions

The recorded waveform file complies with the COMTRADE 2013 standard and can be analyzed using SIGRA software for dual end distance measurement

In the trial operation phase after replacement, it is recommended to configure a waveform recorder to capture a typical fault (or simulate a short circuit manually), compare the timing of the new and old protection actions, and confirm that the difference in protection outlet time is within the allowable range (the minimum tripping time of SIPROTEC 5 can reach 9ms, which is about 40% shorter than SIPROTEC 4).

Part 6: Best Practices for Network Security and Operations

6.1 Activation of Role Access Control (RBAC)

In the era of SIPROTEC 4, simple password protection is commonly used, while SIPROTEC 5 supports RBAC that complies with NERC CIP and BDEW white paper requirements. After replacement, it should:

Configure a Radius server or Microsoft Active Directory for centralized user authentication

Assign minimum permission roles (such as read only, operator, administrator)

Enable security event logging (Syslog sent to central server)

6.2 Firmware Signature and Secure Boot

All SIPROTEC 5 firmware files are digitally signed by Siemens, and the device's built-in encryption chip only loads legally signed firmware, effectively preventing malicious tampering. During the replacement process, it is essential to download the latest firmware (V8.40 and above) from Siemens official and verify the hash value.

6.3 Utilizing SIPROTEC Dashboard for Remote Monitoring

The replaced SIPROTEC 5 device can be connected to the MindSphere cloud platform through the OPC UA PubSub protocol, using the SIPROTEC Dashboard application:

Map view displays the geographical distribution of all protected devices

Fault records automatically uploaded to the cloud, supporting remote analysis

Wear statistics of circuit breaker contacts (∑ I ² t) and monitoring of transformer hot spot temperature

Global comparison of firmware versions to promptly identify devices that have not been upgraded

For cross regional power grid companies, this feature significantly shortens the fault response time.