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Standards and compliance for time synchronisation: IEC 61850, C37.238, MiFID II, IEC 62443

Which standard requires which time accuracy, and which Masterclock solution meets it? Overview of IEC 61850-9-3, IEEE C37.238, MiFID II RTS 25 and IEC 62443, traceable to UTC.

Choose your reading level

Many sectors are legally or normatively required to keep their time provably correct. A trading venue must be able to prove its timestamps fall within a margin of UTC; a high-voltage substation must keep its protection devices aligned to microseconds. "The clock was about right" is not enough there: you must be able to demonstrate it.

Four standards come up most often:

IEC 61850-9-3 (Power Profile): time synchronisation in digital high-voltage substations.
IEEE C37.238: the related profile standard for the power grid.
MiFID II (RTS 25): timestamps for financial trading in Europe.
IEC 62443: cybersecurity of industrial systems, which includes the time source.

Which of these applies to you determines which time server you need. Not sure? Ask for advice.

Traceable, provably correct time is a standards requirement in many sectors, not a luxury. This guide sets the four key standards side by side: what they require and which Masterclock solution meets them.

Why compliance is about traceability

Compliance means you can demonstrate that your time is correct, traceable to the world standard UTC through a known structure. That requires three things: a reliable source (GNSS, disciplined oscillator), a documented chain (stratum, protocol) and a quantified uncertainty. See stratum levels and reliable time.

The standards in one table

Standard	Sector	Core requirement	Masterclock
IEC 61850-9-3 (Power Profile)	Energy / high voltage	PTP time, us class, traceable	GMR6000
IEEE C37.238	Power grid	Power Profile PTP across the grid	GMR6000
MiFID II RTS 25	Financial trading	Max divergence from UTC per activity	GMR grandmaster + PTP
IEC 62443	Industrial cybersecurity	Secure, traceable time source	All, hardened configuration

## IEC 61850-9-3 and IEEE C37.238 (Power Profile)

In a digital high-voltage substation, protection and measurement devices (merging units, IEDs) share the same time at the microsecond level. IEC 61850-9-3 defines the PTP profile; IEEE C37.238 is the related profile standard for the grid. The GMR6000 explicitly supports both. In depth: Power Profile IEC 61850-9-3 vs IEEE C37.238 and IEEE 1588 vs IEC 61850.

MiFID II (RTS 25)

For financial trading in Europe, MiFID II (technical standard RTS 25) prescribes a maximum divergence from UTC depending on the type of trading activity, plus traceability and logging. A GMR grandmaster with PTP delivers the accuracy and the auditable chain. See the financial trading application.

IEC 62443

IEC 62443 covers the cybersecurity of industrial automation. The time source is part of it: it must be reliable and secure (hardened configuration, controlled access, redundant source). Our time servers are configured accordingly.

From standard to choice

Once you know which standard applies to you, the time server follows. Not sure yet? Read the NTP/PTP time server decision guide or tell us your requirement.

Compliance is a question of traceability and uncertainty, not accuracy alone. Each standard defines a maximum divergence from UTC and a demonstrability requirement; the time infrastructure must deliver both across the full chain.

IEC 61850-9-3 / IEEE C37.238

IEC 61850-9-3 defines the Power Utility Profile of IEEE 1588 (PTP) for digital substations: an end-to-end accuracy in the us class between grandmaster and the connected IEDs/merging units, with peer-to-peer transparent clocks and a defined BMCA. IEEE C37.238 is the related power profile standard. The GMR6000 provides a grandmaster disciplined to roughly 30 ns from UTC; the achievable end accuracy depends on the full PTP chain (switches, asymmetry), not the source alone. See Power Profile.

MiFID II RTS 25

RTS 25 sets the maximum divergence from UTC and the timestamp granularity per type of activity (stricter for high-frequency trading than for manual orders), plus a mandatory traceability to UTC and logging. The design implication: a disciplined grandmaster, PTP to the trading servers, and a documented measurement chain with an uncertainty budget.

IEC 62443

IEC 62443 treats the time source as part of the industrial security architecture: authenticity and availability of time, hardened configuration (disabled unused services, controlled access) and redundancy (dual source, holdover) so that an attack or failure of one source does not compromise the time. See reliable time.

The chain determines compliance

No standard is met by the grandmaster alone: antenna placement, switch jitter, path asymmetry and logging all determine whether you demonstrably meet the requirement. Design and document the full chain. See installation.

Sources: IEC 61850-9-3; IEEE C37.238-2017; ESMA RTS 25 (MiFID II); IEC 62443; IEEE 1588-2019; NIST Time & Frequency Division.