High frequency current components can saturate the RCD, preventing detection of 50Hz residual currents. So question one does it pass when tested with a RCD tester? If so what makes you think it is faulty? I am sure the one in my old house was tripping due to surges when a neighbour was welding. Two identical RCD's would hold for 18 months without a problem, then trip for seeming no reason for couple of weeks, then again two years no tripping. The revised RCD guidance in 531.3.3 is precise. The appropriate Type of RCD must be selected, based on the characteristics of the residual current and the equipment that is likely to be connected to the RCD protected circuit.

A well-timed subject. Just a few weeks ago I tried to find a new RCD to replace an old BS4293 one. I have seen how a pure type-AC RCDs rated for 30 mA trip can allow multiple amps of half-wave-rectified current without tripping. As this is a TT installation where earth fault protection depends on the RCD, it feels very inappropriate to have anything less than a type-A, given that plenty of loads contain rectifiers. (Admittedly, the old one was presumably only like type-AC, but that's not an excuse.) It should be noted that a pass of the EMC standards required for CE marking is a very easy standard to pass, and does not require anything like enough protection to guarantee co-location of equipment. The prescribed levels are set so that you are unlikely to receive or cause trouble from or to the neighbours next door, rather than to prevent self interfernce between bits of kit on the same property, where supposedly you are able to do something about it yourself. The fault current (If) contains mixed frequency components between 10Hz (minimum motor frequency) and 1kHz (maximum inverter switching frequency) ***. I believe the article makes it clear that the their are 4 Types of RCD that may need to be considered - Quote from the article -

Type F RCDs cannot provide protection in circuits where there is a requirement to detect smooth DC residual currents, or if the motor frequency can be reduced to zero or the inverter switching frequency is >1kHz. If any of the above conditions apply, Type B RCDs must be used. Memshield 1 – These are a commercial breaker and come in various types (Type 2,3,B,C & D) depending upon the age. Most are M9 rated. Type AC RCDs are in clause 531.3.3 of BS7671 2018, because they are still in EN 60364-5-53 2015. The UK have just adopted this line from the EN standard. Would you be able to reveal the make and model of the RCD that trips, and the make and model of the smart meter?

is the 100a 30ma RCD a main isolator for the whole of the fuse bord or is it just protecting part in a split-load arrangment. This handy RC Unit (residual current unit) has been designed for installing on to any standard 1P or 1P+N Eaton MCB with a 10kA, 15kA & 6kA rating to create an RCBO. The MR30 RC POD unit is ideal for standard applications with a 230-240 VAC voltage rating and 30 mA breaking capacity and is field fitable. Fully compliant with Standard 61009, this capable MR30 POD is utilised in numerous industrial and commercial applications due to its versatility and ease of assembly. You might ask "Why are Type AC RCDs still referred to in the 18th Edition of BS7671, when most installations should be using Type A devices as a minimum requirement?"

UK electricians can still make informed technical decisions

In some other countries in Europe (perhaps not coincidentally the ones commonly using 3-phase supply to homes), it's much easier to find type-A or even type-B. It is more a physical size & shape of fitting onto the Din rail inside the fusebox & if the main live bus-bar has a blade or a fork type fixing to the RCD and each MCB. Requirement for a transient resistance feature < 3 kA and short 10 ms time delay. **Note: Type A transient resistant RCDs only meet EN 61008/9 for general UK 50Hz residual currents. RCD failing to trip when the appliance is running, and the RCD test button is operated, could be an indication that the appliance is affecting the RCD.