The smart grid concept aims to improve power systems’ robustness, efficiency, and reliability. Thetransition from conventional power grids to smart grids has been achieved mainly by integratingSmart Electronic Devices (SEDs) and advanced automatic control and communication systems.On the one hand, electronic devices have been integrated to make the system more decentralisedfrom the national electrical grid. On the other hand, from the point of view of protection and controlequipment, there is a growing tendency to replace arrays of analog devices with single digitalunits that perform multiple functions in a more integrated and efficient way. Despite the perceivedbenefits of such modernisation, security issues have arisen with substantial concern as electronicdevices can be susceptible to Intentional Electromagnetic Interference (IEMI) [2].The number of IEMI sources has grown significantly in recent decades. In 2014, 76 different typeswere reported, in which 21 sources were conducted, and 55 were irradiated. From a technicalperspective, they can present different features, including band type, average / centre frequency,peak voltage (for conducted sources), or peak field (for irradiated sources) [4]. These sourcesalso differ in technology level, associated cost, and mobility in approaching the target system.Therefore, they can be characterized by the easiness of occurrence in a given scenario and theincreased probability of successful attacks on a target system. Under this perspective, a self-builtjammer built with off-the-shelf components is more likely to be employed by an offender than aHigh-Power Electromagnetic (HPEM) source. On the other hand, despite being less probable onaccount of higher technological level, cost and mobility, a HPEM source may have a higher successrate to affect the target system than the self-built jammer. Coupled with this, based on the differentcharacteristics of the IEMI sources, the electronic devices may present distinct effects, which maytrigger severe impacts on a smart grid at a higher level [8]. Therefore, this study compares the IEMI vulnerability of three devices used in smart grid applications.The first device is a Wi-Fi-based smart home meter. It can read voltage and current signalsof consumer units and remotely display real power, reactive power, and power factor. These measurementscan be used in-house or transmitted to a Supervisory Control and Data Acquisition(SCADA) system from Distribution System Operators (DSOs). The second device is a Power LineCommunication (PLC) unit, which enables data to be carried over conductors intended primarily forelectrical power transmission. This technology is used in buildings to reduce the communicationnetwork’s material and installation costs and provide flexibility and faster data communication. Thefinal device considered is a digital protection relay designed to trip circuit breakers when faults aredetected. The latest digital relay units feature many protection functionalities, including overloadand under-voltage/over-voltage protection, temperature monitoring, fault location, self-reclosure,among others. The three devices are subjected to self-built low-power jamming signals. As anextension, the protection relay is also subjected to a narrowband High Power Electromagnetic(HPEM) source.