Siemens 7SJ80, 7SJ82, 7SK80 and 7RW80 (SIPROTEC) Relays

What it is and where it is used

The Siemens SIPROTEC 7SJ80 relay and its siblings 7SJ81, 7SK80, 7SK81, 7RW80, 7SD80 and 7SC80 make up the SIPROTEC Compact family, which Siemens sums up as “perfect protection in the smallest space”. They are numerical relays for medium-voltage networks and for industry: distribution switchgear, motor panels, transformers and outgoing feeders at generation plants. To go further: Siemens 7SK82, 7SK85 and 7SK80 relays.

Siemens states that the 7SJ80 serves feeders and lines of high- and medium-voltage networks with solidly grounded, low-resistance grounded, isolated or compensated neutral, and that it has everything needed to act as backup to a transformer differential. For the general picture, see protective relays.

Variants of the SIPROTEC 7SJ80 and its family

Siemens also now uses the name 7SJ81 for a compact device of the SIPROTEC 5 family. Before ordering a spare or a settings file, confirm the platform from the order number on the nameplate.

Main functions

According to the SIPROTEC Compact catalog (SIP 3.01, edition 5):

The 7SJ80, 7SK80 and 7RW80 also bring “flexible protection functions”: up to 20 additional functions that the user builds from measured quantities.

Communications and integration

The Compact family supports IEC 61850 (Siemens states compatibility between editions 1 and 2), with GOOSE messages, an integrated switch for rings and RSTP, PRP and HSR redundancy (guide). It also offers IEC 60870-5-103, IEC 60870-5-104, DNP3 TCP, Modbus RTU and PROFIBUS-DP, depending on the communication module installed. Configuration and evaluation are done with DIGSI 4; fault records are viewed with SIGRA. The 7SJ82 uses DIGSI 5.

7SJ80 hardware and order code

According to the catalog, the 7SJ80 comes in a 1/6 19-inch rack housing, 244 mm high, designed to replace earlier models. The order number (MLFB) combines, among others, these fields:

• Measuring inputs: four current inputs and, depending on the variant, three voltage inputs. The ground input can be normal (1 A or 5 A) or sensitive (0.001 to 1.6 A with 1 A, or 0.005 to 8 A with 5 A), useful on isolated or compensated networks.
• Binary inputs and outputs: 3, 7 or 11 binary inputs and 5 or 8 outputs, two of them changeover (C contact), plus a device live contact. The binary input thresholds are set by software at three levels. On this point, read case of a project opened with another software version.
• Auxiliary supply: 24 to 48 V DC, or 60 to 250 V DC with 115 or 230 V AC, depending on the order number.
• Mounting: surface or flush mounting housing, with screw terminals.
• Region and language: the catalog lists variants with texts in German, English, US English, French, Spanish, Italian, Russian and Chinese (the latter does not allow changing the language).
• Ports: port B (lower) supports modules such as IEC 61850 with two electrical or optical Ethernet ports, and combinations of IEC 61850 with DNP3 TCP, IEC 60870-5-104, Modbus TCP or PROFINET. Port A, with Ethernet, is used for DIGSI and for extension with SICAM I/O 7XV5673 units.

The current and voltage terminals are plug-in, and the CT secondaries are short-circuited in the removable block itself, so a secondary cannot be opened when it is withdrawn. This makes pre-wiring and replacing the device easier, but it does not replace the safety practices for the current transformer.

What changes between the 7SJ80, 7SJ81, 7SK80 and 7RW80

The catalog includes a function table by model. The differences that matter most when choosing or replacing:

• 7SJ80: in addition to 50/51, it offers directional 67 and 67N, sensitive directional ground 67Ns, reclosing 79, synchronism check 25 and fault locator, depending on the variant and the voltage inputs. It includes inrush current detection, cold load pickup (51C) and four settings groups.
• 7SJ81 (Compact): same overcurrent function, but with inputs for low-power current transformers (LPCT). Siemens states that primary rated currents from 20 A to 2500 A are covered depending on the LPCT ratio chosen: for example, 300 A/225 mV for an operating range of 60 A to 630 A.
• 7SK80: adds locked rotor (14), starting time supervision (48), restart inhibit (66) and temperature monitoring. It supports connecting up to two temperature sensor boxes (RTD) with a maximum of 12 sensors. It does not include reclosing or phase directional. For the motor context, see motor protection relay.
• 7RW80: voltage and frequency protection with overexcitation (24), vector shift, voltage and frequency derivative, and load restoration (81LR), intended for load shedding and separation. It has no overcurrent protection.
• 7SC80: up to 16 settings groups and feeder automation functions; it is the only one in the catalog table with optional single-pole tripping.

Busbar protection with reverse interlocking

The catalog shows a frequent distribution application: busbar protection by reverse interlocking with overcurrent relays. When a feeder relay picks up, it sends a block to the short-time function of the incomer relay, which trips fast (the catalog example uses 50 ms) only if no feeder saw the fault. Siemens limits it to distribution busbars with no significant infeed from the feeders (less than 0.25 times the rated current). The block can travel through contacts or through IEC 61850 GOOSE messages. In the field, watch the time coordination and the supervision of the blocking signal, because a lost signal can leave the busbar without fast tripping or block by mistake.

Frequently asked technical questions

• 7SJ80 or 7SJ82 manual: they are different manuals, one per platform. Using the wrong one leads to looking for parameters that do not exist.
• 7SJ82 drivers and USB connection: if the device does not appear over USB, the port driver or the DIGSI 5 version that matches the firmware is usually missing.
• DIGSI 4 does not open the file: the DIGSI version and the device package must match the firmware.
• Ground fault on isolated or compensated networks: the detection method depends on the neutral; there is no universal setting.
• Trip on energizing downstream transformers: see overcurrent trip on starting or energization.

How we can help

At Tiza Group we remotely configure SIPROTEC Compact and SIPROTEC 5 relays with DIGSI 4 and DIGSI 5, worldwide: protections, allocation matrix, CFC logic and IEC 61850, based on your study and the approved settings. See the scope in remote configuration of Siemens SIPROTEC relays. If your 7SJ80 or 7SK80 tripped and the reason is unclear, we quote a trip analysis. For anything else, write to us through the contact page.

Related guides

• Siemens DIGSI 4 and DIGSI 5 software
• SIPROTEC 7SJ85 relay
• SIPROTEC 7SA87 relay
• Line differential protection 87L
• Phase and earth overcurrent protection
• Automatic reclosing 79
• COMTRADE files
• Case: project opened with another software version
• Siemens 7SK82, 7SK85 and 7SK80 Motor Protection Relays

References

• IEEE C37.2, device function numbers.
• IEC 61850 (series); IEC 62439-3 (PRP and HSR); IEC 60870-5-103 and 104; IEEE 1815 (DNP3).
• Siemens, SIPROTEC Compact catalog SIP 3.01 (edition 5) and 7SJ80 and 7SJ82 product pages.

Frequently asked questions